WoWDB

DO NOT STAND IN THE DEFILE. Also, kill the val'kyr as fast as possible before they drop their captured player over the edge. The val'kyr can be snared and stunned. Or, if you were in Ensidia, you just used  Saronite Bombs.

If you are doing this at level 90, the only mechanic that is worth caring about is  Fury of Frostmourne. It is survivable if you have the right cool-downs. Paladins can bubble and hunters can use Deterrence. I've seen warlocks survive but I'm not familiar enough with their class to know what CD(s) they use. Same for guardian druid. Mages, Ice Block does not work. :(

Also, if you cause the Lich King to skip transitions and get him down to 1HP before or during his role-play speech, King Terenas II will not resurrect dead players at the end of the Lich King's speech.

Warlocks can use  Unending Resolve, immediately followed by  Dark Bargain. Since the Lich King has a lengthy dialogue, it is simple enough to heal the delayed damage using  Drain Life.

Guardian druids can utilize  Survival Instincts.

But if doing this at level 90, chances are you will burn down the Lich King while he's in the middle of the transition phase. So if you are able to survive Fury of Frostmourne, mind the AoE from Remorseless Winter.