We use 3 tanks on KT and 6 rogues.

MT
OT 1 +2 KT 3 Rogues
3 Rogues

This enables max melee dps, 3 tanks to counter MCs and enough room to make sure the frost blocks arent chained. If a frost block hits a rogue spot shamies NS-CH.

AS we're horde we also try to have shamies in shock range to spamm ES rank 1, especialy after a MC as the melee can have problems interrupting.

Rest of the raid spread out, group wise for PoH ofc.

Fase 2 is really easy except for the MCs, so make sure everyone stops dps when a MC comes and the tanks get KT back into position asap. A rogue might wanna hit evasion and keep on hitting, also for interruption, if KT stays in position the tanks will get him back fast enough.

Most important in Fase 3 is that you keep on going as in fase 2, if people start to run around or do other things you will not make it, dps will either be to low or people will kill eachother with mana detonation/frost block chaining. Priests shackle, the other warriors in the raid tank adds and the rest of the raids keeps on going as if its still fase 2.

As far as Mind Controls are concerned, they appear to be a raid wide aggro clear (think Noth's Blink). So, having a tank just shieldslam after a MC will grant him aggro. Obviously you need your DPS to slow down after MC is available (45s cooldown). I'm assuming your DPS that is pulling aggro is probably after an MC, and because of DoTs or spells midflight.

For Interrupting single target frost bolts, we simply put 2 melee on a 3 pair rotation, (Interrupt #1, Interrupt #2, Interrupt #3) saving counterspell for Interrupts during Frost Blasts (where we have melee spread out) and MCs. You need to have people topped off before every single frost blast, so that a single heal/shield will keep them up if needed.

We do not use frost resist on tanks or DPS, however since sapphiron we have been able to run pretty priest heavy.

Hope this helps.

We use 3-4 tanks on Kel'Thuzad and 2 rogues which take turns at kicking (The tanks bash whenever they can) The other 4 rogues are cheering on their respective spots, shooting with their guns and bows and bandaging themselves. When a frostblast hits, they come jumping into melee with KT aslong as the tanks have him under control and are not being MCed.

If the 2 rogue interrupters get MCed/Frostblasted, a third designated rogue goes in and kicks while they get out of MC/frostblast.

Whenever an MC occurs on more than one tank, everyone stops their DPS until control is back, naturally. The 2 interrupters stop attacking and just run _WITH_ KT and kick whenever he is about to cast his bolt.

When PC first killed Kel'Thuzad, we were pretty clueless on the fight. It took us a full 2 nights of raiding to kill him (Previous attempts were latenight tuesdays after a sapphiron kill where we wiped in p1. Furthermore, at the first kill we had every single rogue on him and for some twisted reason we managed a 1% wipe and a kill on that very same day with 6 rogues on him. Looking at it now, it would be obvious suicide to have that many people at one spot, practically begging for a frostblast on us (and thus a shitload of dead rogues). Don't do that. Don't count on luck.

Edit: None of us uses frost resistance either. Would be interesting to test it out on certain classes though.

Frost resist gear is nice in some situations. A lot of it depends on the type of raid you take. We usually have people wear ~100 frost res buffed. Even though the frost bolts aren't partially resistable, getting that full resist every once in a while may help the healer in your group conserve some mana (especially if its a druid).

There's a ton going on during the fight, so the easiest way to go at it is to find your problems and find solutions for them one by one. I think our 3 biggest problems were:

Mind control causing KT to run wild and kill someone. Sometimes people run around like crazy and we get a terrible frost blast that hits like 5-6 people. You said you were having trouble controlling MCs, so this seems like a similar problem.

We use a rather different setup than the last few people that posted here. We have 3 groups around KT, each group has 1 warrior and 2 rogues and stands in a triangle form so they dont chain eachother. That way, even if KT does run in a direction opposite of the MT, he's always running towards one of the tanks and you don't have the whole tank running behind KT out of range as he rails some warlocks. Even if someone does get a spell off, a shield slam plus a lot of saved up rage is often enough to rip it right back and keep it (yes, we have salv). Also, on a MC, he may move a bit, if its anywhere near a frost blast, tell your rogues not to panic and sit in their spots while the tank brings it back into the spot. Have mages use their CS and/or rogues in range of him do the kicking. It gets incredibly bad incredibly fast if you get 2 melee groups frost bolted.

Some people think 3 people iceblocked is pretty harsh in melee range. Though if you set your dps groups such that each one of those 3 people is in a different group, their group healer should be able to keep them up.

I kinda covered our 2nd problem in there too, its rogues and other melee classes getting frost blasted in masses and dropping like flies. Just make sure they're calm and don't bunch up if there's a frost blast coming for any reason. If we have more than 6 rogues, any extras just get to sit out until a frost blast, then run in and poke KT a few times.

The biggest problem we had, and I think everyone else has had, is the adds coming in at 40%. Do we shackle? Do we offtank? The offtank got MC'd, the offtank got frost blasted, the priest shackling got railed... etc... Things get out of control really fast once those guys spawn. And to be honest, we still don't have a good way of handling it. If we get some decent luck in MCs and frost blasts, he's low enough when it starts spiraling outta control that we can kill him before he kills us.

We currently have 3 tanks assigned to pick up adds, and 3-4 priests assigned with individual marks to shackle anything that runs around. So they shackle it, and mark it right after so they know which ones theirs. I'm sure someone could elaborate more on that phase though.

We shackle 3 and OT 2.

Also remember priests have to focus on that one Shackle, don't ever Shackle and switch targets the aggro will stick on that priest and he'll probably get 2 shotted very shortly after. What I mean is don't Shackle then have a tank come and try to grab the aggro off it, just let the priest handle the shackle once they have it.

Usually best to assign priests who will be responsible for shackles based on location. The adds can only spawn in the 4 spots... if a tank can pickup 2 and you can keep him up no problem go for it.

And many people have pointed out, continue to stop all DPS on MC until a new tank has it.

We typically run with 5-6 warriors in raid on KT.