The big killers during KT:
1. Frost blast killing multiple groups of melee
2. Frostbolts killing too many players
3. Mind controlled players killing other players
If you manage those and then succesfully shackle 3 + tank 2 of the final adds, it's usually a kill.
For 1, try splitting into 3 groups - left side, behind and right side. If a single group gets hit it means lower numbers for the healers to keep up, but you run the risk of chaining multiple groups if players have poor positional awareness.
For 2, use curse of tongues and make sure all rogues use kick.
For 3, make sure mages and warlocks have /targetenemyplayer macros for firing out quick CC. Also encourage warriors to intercept or intimidating shout and rogues to blind or gouge if they spot players not CC'd.
It's also wise for warriors and rogues to save all major cooldowns for the final phase so you can burn KT down as quickly as possible.