I would really like to do some detailed guides; however, the normal mode Dragon Soul fights have been disappointingly easy so far. Thus, I'll write some short rundowns.
* - The Hagara rundown is not especially brief; whoops.
My guild one-shot this boss. It's ridiculously easy. Start the fight by moving in close to the boss; this is to help soak the damage of "Stomp", which splits damage between all players within 25 yards. Not that you'll be the closest person...but don't be the closest person, as you might take twice the damage.
Otherwise, your personal responsibility will be to deal with "Resonating Crystals". Three of them will spawn in succession, dealing damage to three targets based on how far away they are; the closer you are, the lower the damage. Ranged need to deal with this, so be expected to run around a bit. If you have procs of Fingers of Frost/Brain Freeze, or are close enough to touch the crystal within one global (use Fire Blast), then cast some spells as you move to the crystal. Otherwise, Blink your way over.
Occasionally, Mor'chok will pull the entire group next to him, damaging them for 5% of their max health. After that, a bunch of stalagmites appear from the ground, and you'll need to run (or Blink) behind one before he casts "Black Blood of the Earth", which covers the ground in nasty stuff that will hurt you...a lot. As ranged, you can still hit hit Mor'Chok during this phase in two ways:
1. If you jumped behind two stalagmites, you can position yourself between the two and fire at him from there, or
2. You can get Line-of-Sight on Mor'Chok by moving just barely past the edge of the stalagmite, standing as close to the blood as possible.
If your Frostfire Orb is off cooldown or about to come off cooldown, you are going to want to choose option two. This is also a good time to use Time Warp, or your Volcanic Potions.
After this phase is over, stack in again, rinse and repeat.
As a Frost Mage, I don't believe you bring much special into this fight. Arcane will rule the burn phases, and Fire can keep up their DPS while moving. Granted, you're not doing so bad, given that you can theoretically keep up maximum damage while moving, and your single-target damage still isn't even bad. It might be best to save Frostfire Orb and Pet Freeze for this reason.
For Glyphs, I recommend taking Ice Barrier, Evocation, and Blink. Blink gives you the best mobility, while Ice Barrier and Evocation are just for general survival.
This is an easy fight as well...for DPS, at least. Yor'Sahj spawns three different colored adds (of six possible) that make their way to him. You can only kill one, and the other two are going to grant him abilities. Your raid leader will decide which one the raid is going to kill, so don't try and rambo a different one...I don't need to tell you that, right? Otherwise, go back to killing Yor'Sahj after the add is down. He will spawn new adds and gain new abilities every once in a while, so you'll have to know your own special contingency plans for all six abilities. Here's some things you need to know, based on which colored adds reach the boss:
Red: You're going to take damage based on how far away you are, so stack in close to the boss.
Green: You're going to take damage if you're too close to other raid members within 4 yards, so try and spread out a bit.
Black: There are going to be adds that need to be AoE'd down, so you're going to stack in on the boss. For this very reason, I would recommend having a spec that takes Impact instead of Netherwind Presence, as well as Glyphing for Frost Armor.
Yellow: If you don't use Ice Barrier much...this is one of those times where you should start. P.S: Start using Ice Barrier.
Blue: You're going to have your mana drained and placed in an add which runs around the room. Save your Mana Gem (and Arcane Torrent if you're a Blood Elf) for this, and switch to Mage Armor (or Frost Armor if Yor'Sahj got Blue+Black). Once the add is down, it gives mana back to RDPS/Healers within 15 yards, I believe? You have to be pretty close. Once that's done, do whatever needs to be done to handle Yor'Sahj's other ability.
Purple: Well, you don't have to worry about this much, per se, but this phase makes it more dangerous to heal you in general, so make sure you're casting Ice Barrier (and Mage Ward if Yor'Sahj got Purple+Red).
As a Frost Mage, your advantages lie in having Ice Barrier to help take some heat off the healers. You also have better AoE than Arcane, again putting you in sort of a middle ground of mobility vs. single-target damage between Fire & Arcane.
For Glyphs, I recommend Ice Barrier, Frost Armor, and Blink. Ice Barrier is taken for survivability, and Frost Armor is taken to mitigate damage from the adds while being able to run your AoE without running out of mana. Finally, Blink is used to move back to the boss after killing the adds, which spawn pretty far out. You can still attack Yor'sahj while moving out to the add, so I recommend using it to move back to the boss, rather than moving out towards the add.
This fight actually requires some attention on your part. The main mechanic of this fight is the boss spawning a "Void of the Unmaking", a giant purple volleyball which needs to be bounced between two groups - melee and ranged. Most raid groups will aim it at ranged first, so you'll need to watch for the ball forming and get in front of it right away. Being in front of the ball causes it to bounce in the opposite direction and deal damage to anyone within range. This also means that your groups need to move as one, and be on the ball - no pun intended - about moving in the way of its trajectory.
The ball deals more damage every time it's bounced, so you'll eventually need to pass it to Zon'ozz himself (exactly how you do this is up to your raid - we had melee move back while the tank kited the boss into it). This begins a burn phase, where the entire raid takes damage for a little while. Zon'ozz takes more damage based on how many times the ball was bounced before you pass it to him, so this is a good time to rock your cooldowns. If you're using potions or are in charge of Bloodlust, make sure you know how many times you're going to bounce the ball each pass; for example, my raid did 5-5-3-3-etc. so it would be most efficient to use them on the first burn phase.
The only other important thing to know, is that while the ball is being passed around, Zon'ozz also casts a DoT on random players called "Disrupting Shadows", which ticks for high damage, but also hits for huge damage and knocks back upon being dispelled. If you get hit with this, try and run out of the group, because you will almost certainly die if you hit the ball at the same time that it gets dispelled.
As a Frost Mage, your advantage is quite clearly in your ability to mitigate damage. The raid damage on this fight is pretty intense, and the fact that you have Ice Barrier is a huge benefit to the group; be sure to use it on cooldown.
On the other hand, you might even be at a slight disadvantage based on the shorter range of your spells. If your raid group has an unusually high amount of RDPS, you might ask to be put in the melee group. If you have to move out of range to hit the ball, be sure to turn on Mage Armor, as it will help mitigate the damage; you can switch back to Molten Armor as you move back in range.
For Glyphs, I recommend Ice Barrier, Evocation, and Blink. Ice Barrier should be a no-brainer for survival. Evocation's heal can be used as an emergency precaution. Finally, Blink is useful for stacking in during the burn phases or moving back out afterwards, if you have no procs to spare.
This fight sounds pretty scary at first, but it's actually easy. Hagara has three attack phases: Main Phase, Ice Phase, and Lightning Phase. The flow of the fight is: Main, Ice/Lit, Main, Lit/Ice (in other words, the second phase is random between Ice or Lightning, and then the fourth phase will be the alternate).
In the Main Phase, your primary concern is the Ice Lances (hers, not yours). They will shoot from the edges of the room, and need to be blocked by Healers and RDPS; the reason being that they place a buff on their target which slows Melee attack speed. She'll also use Shattered Ice, which hits a random playing for 70-80K damage. This damage can all be reduced by Mage Ward as well as Ice Barrier, so give your healers a hand.
Every Main Phase after the first one, Hagara will use Icy Tomb on two random players, freezing them in a block of ice where they take periodic damage. Your priority is, naturally, to break players out of the tombs rather than DPS Hagara.
Next, will be the Ice Phase or Lightning Phase. Let's talk about Ice first:
When Ice Phase begins, Hagara shields herself, and you will only be able to move in the outer ring of the platform. Four "Binding Crystals" will spawn in the North, South, East, and West points of the platform. A few seconds after that, Hagara summons an Ice Wave, a rotating "X"-shaped wall of ice that will probably one-shot you if you get hit by it. All four Binding Crystals need to be destroyed to stop Hagara's Ice Wave and lower her shield.
Now, a lot is made of how Fire rules this phase due to their ability to move and cast; perhaps rightfully so in the Heroic version. However, in Normal mode, the crystals drop FAST, and so I think that Frost has an excellent advantage here: we can attack THREE crystals at once. Here's how you should be doing the Ice Phase as Frost:
1. Pick a crystal that you want to target and Blink slightly to the right of it. For example, if you choose the north crystal, Blink towards northeast.
2. Throw your Frostfire Orb to the Crystal to your right side (going with the example in step 1, you'd be throwing this at the East crystal, since it would be to your right).
3. Now, move towards your preferred crystal and stay slightly to the right of it (but not exactly in-between, cos that's exactly where the Ice Wave spawns, and you'll die. A lot.). Cast Pet Freeze on it as you move into position if you have no Fingers of Frost charges.
4. Order your Pet to attack the Crystal to your left (i.e. we chose to target the North platform, so your Pet will be attacking the West Crystal).
Congratulations, you are now hitting three out of four Crystals. To clarify something, you want to stand to the right of the crystal you're targeting, because the walls of the Ice Wave spawn at the midpoint between two Crystals and rotate clockwise. Thus, if you stand slightly to the right, one of the walls will spawn right behind you, and move away from you, allowing the most possible time for you to stand in place and shoot.
While you do this, take the time to look at the adjacent Crystals:
If the one to your left is going down, run clockwise (same direction of the Ice Wave and get ready to shoot the next Crystal you run by. You can Blink towards it to get some additional stand-in-place time. Keep moving clockwise until all of the Crystals are destroyed. Be sure to keep track of whether or not your Water Ele is still attacking a target.
If the one to your right is going down, rejoice - you are one of the only classes who can move contrary to the Ice Wave thanks to Blink and Ice Block. Once your target is down, walk counter-clockwise and Blink through the Ice Wave as soon as you can. Remember, those things HURT, so Cast an Ice Barrier as you run into position. After you've blinked through the wave, get in range of your next target and shoot it; you'll have a decent amount of time to stand and shoot. If you need more time, Ice Block as the next wall is coming your way.
...Oh yeah, and Icicles fall from the ceiling. Don't run through cold-looking circles unless you want to get knocked off the platform and die.
Once the Crystals are destroyed, Hagara is vulnerable and takes additional damage for a few seconds. If you are trying to top the DPS meters, you may wish to save your big cooldowns for this. However, if your raid group is still working hard to beat this fight, it's better to blow up the crystals instead.
The Lightning Phase is way less-complicated than the Ice Phase (on Normal, at least). Hagara shields herself in in the same manner as she does on the Ice Phase, and spawns some Crystal Conductors, along with one Lightning Elemental. Make your way over to the Lightning Elemental and kill it immediately (it should be noted that it spawns near a Conductor and should be killed near the Conductor, but that's the Tank's concern). When it does, the nearby Conductor blows up, and one of the raid members nearby becomes charged with Lightning (debuff is caleld Lightning Conduit). Everyone then needs to move towards the remaining Conductors together; they will be destroyed as you move past them. Be sure to turn on Mage Armor as you run around, so that you can gain as much Mana back as possible.
When all the Conductors are destroyed, Hagara takes additional damage, just like she does after the Ice Phase. After every Lightning/Ice Phase, Hagara repeats her Main Phase.
As a Frost Mage, you're pretty well off in this fight. Fire and Arcane can probably take better advantages of the burn phase than you can, but even in that regard, you'll be pretty well off. Your ability to mitigate damage better than any other spec, your ability to move short distances while casting, and your ability to attack most of the Crystals during Ice Phase makes Frost a pretty good candidate for this fight.
For Glyphs, take Ice Barrier, Evocation, and Blink. Ice Barrier should be obvious. Blink will get you the most possible DPS uptime, and Evocation...cos, you won't be using Frost Armor? I don't know, I don't really run out of mana in this fight!