First of all, I did do less damage than in my fire spec. About 1-2k dps less, depending on fight. I did have the proper glyphs, but on the other hand my entire gear was still gemmed and reforged towards fire, meaning I had tons of crit and reforged everything to mastery. I don't think this is the right way to go for frost however. Also I haven't played frost for a long time and didn't have much practice with getting the right skills used with the right procs and all that. Taking this into consideration I am amazed I only did 1-2k less dps than my fire spec.
I'll start with an overall impression - I liked frost. I definitely sensed potential. Unlike fire it doesn't have a rotation, but is purely proc based. You basically spam frost bolts until you get Fingers of Frost (FoF) or Brain Freeze (BF). These two procs open up a bunch of possibilites for how you'd best want to use them. We can either use Deep Freeze, Ice Lance, Fireball or Frostfire Bolt depending on proc, and which we choose is mostly dependant on whichever does the most damage. I found that whenever you can you'd want to use Deep Freeze. Even with my non-awesome gear (it's definitely not bad, but not "up there") I usually did around 40k damage with Deep Freeze. Whenever your DF is on cooldown you use FoF on Ice Lance. Unless you've simultaneously also procced BF in which case you'd want to use Fireball or Frostfire Bolt instead. I actually found that FFB did more damage than FB, and with the glyph you also get a nice dot on the target. Here are some of the things I'd like to discuss however;
Haste seems to be a better stat for frost, definitely better than crit. With alot of haste we get more FoF procs, and FoF will increase your crit chance with Ice Lance and Deep Freeze by so much that you'll easily overcap yourself if you've got over 30% crit, thanks to the Shatter talent. Shatter will increase your current crit chance on a frozen target by 3, which means if you have 30% crit chance you'll get 90% crit chance against frozen targets. Before you drop that jaw though, remember that frozen targets only counts those affected by Frost Nova/Freeze, which aint gonna happen in a raid. FoF makes Ice Lance, Frostfire Bolt and DF count the target as frozen and this is where we'll deal our real damage. Also we have no bonus from crits, besides the extra damage. What you want are as many Frostbolts as possible, which means you'd want a lot of haste. I did also notice however that Frostbolt already has a comparably short cast time and with bloodlust/heroism you'll come very close to cap. You probably don't want to use Icy Veins when BL/Heroism is up because that would be a waste of haste. This means haste is important but still easily cappable (at least compared to fire, don't know about arcane) and we definitely have to keep an eye on this. Also alot of frost dps are from instants, which further makes haste less valuable. The only thing you have to keep track off is speeding up your frostbolt as much as possible, but not so much so that Icy Veins or BL/Heroism means overcapping too much.
Using my über math skills (*cough*) and wowpedias haste information, I've come to the following conclusion;
Haste rating needed for cap (hrnfc) - 3279
Hrnfc with BL - 2296
Hrnfc with Icy Veins - 2623
Hrnfc with BL and Wrath of Air Totem - 2132
But! With the talent Early Frost we are reducing the cast time of our frostbolt to 1,3 seconds every 15 seconds. Bloodlust alone will cap us when we have this cast time, but we only have it every 15 seconds. During 15 seconds we can expect to cast another ~9 casts (with my current haste) which we would want to be hasted. From those ~9 we'd want to subtract instants that'll proc. How many frostbolts can we expect to cast that need haste between each 15 second intervall? I usually get roughly 4-5 Frostbolt casts between each 15 second intervall, with my current haste of about ~650 rating or ~20%. This tells me that haste is important, but like I said easily capped (by "capped" I here mean "put up to a practical amount"). We probably don't want much more than a maximum of ~1000 haste rating.
Frost Mastery is Frostburn which increases damage against frozen targets. In a raid you can only ever hope to increase the damage of Ice Lance, Frostfire Bolt and Deep Freeze with our mastery, which are the only spells affected by FoF. This means our mastery doesn't affect all of our skills, but still an important part of them. The more haste we've got, the better our mastery becomes it seems, but I am still divided as to just how good our mastery is in the long run. On the other hand once we've got enough haste there won't be much other stats to reforge into.
The second best stat to collect, next to capping haste (at around 1000 haste as discussed), and hit of course, would be to smack on as much intellect as possible. I think most mages will get enough hit and crit from using endgame gear, so what we'd want to gem is haste and intellect.
From my limited testing it seems like we should prioritize like thus;
- Hit (to 17% with buffs)
- Haste (to about 1000 rating)
The pet doesn't make much of a difference. Unlike most other pets it brings no buffs or good amount of damage and whether you've got it out or not during a boss fight won't make much of a difference. I see potential in the talent Improved Freeze which makes your pets Freeze skill proc two FoF for you. This means you could get two FoF procs at will by using your pets freeze skill. I didn't try this talent and don't know if you'll get the procs even if you're freezing something that is immune to freezing, like a boss. I am assuming you do, otherwise this talent is purely a pvp talent. If it does work however it brings further depth and necessity of skill to frost dps.
Cold Snap is a lovely talent since it allows you to use Ice Block twice during a fight and Icy Veins one extra time during a fight. Knowing when the best time is to use Cold Snap will definitely make a difference.
When we get BF procs, do we want to use FFB or FB? Like I mentioned I noticed that FFB seemed to do more damage, especially when glyphed. This is because it is affected by FoF. One idea could be to use FB whenever you've got 3 stacks of FFB up already and no FoF proc. This would probably be the ideal damage, but quite tricky to manage. Also you never really know when you'll get another BF proc and you don't want your dot stack to drop either. Tricky indeed.
Although frost mages don't have a good skill to use when running, like fire mages do (scorch) I didn't feel like running was much of a penalty. You've often got some FoF procs to use up and this could be a good time to use your pets Freeze for some extra FoF procs, which will allow you to use instants on the run. Just using an unprocced Ice Lance is basically useless as it deals close to no damage that way.
Mana is definitely less of an issue for frost mages than fire mages. I didn't have much trouble in the various fights we did in ICC. As a fire I usually oom very fast, as frost I think mana consumption was reasonable. I still often had to use Mana Gems, but I never found myself completely out of mana.
These are just some quick notes on frost dpsing in raids. It's not as good as fire or arcane right now, but challenging and fun. If you're currently raiding mostly for fun, and doing fights where you don't need everyone to be at their max potential, I definitely recommend at least trying it out. Mastering frost dpsing seems to be the trickiest among all the mage specs right now and it's really not far behind the other specs (especially not when compared to prepatch).