This is a classic mistake. What stacks on the Lich King is Plague Siphon, but what you need to stack to 30 for the achieve is Necrotic Plague. Which is what jumps between the adds and the players. Ignore the numbers on the Lich King and count the highest stack (you'll get more than one Necrotic Plague jumping around) on the adds.
1 tick from a high stack of plague will instantly kill him (^^_)
Edit: If there is alot damage on the adds. You might end up needing sum1 to grab the 28 - 29 stack and get it cured.
Tank should only use taunt and any looooooooow damage threat abilities to keep just above healers.
Keep a backup dps/healer for that extra tick.
I took 30th tick from tank and cloak of shadowed it in the corner away from every1 else
Last edited by Sanguinezor; 2013-04-10 at 07:32 PM.