Illusionist
Ordered by importance.
Main:
Mana Flow
Cure Arcane
Assist
Synergism (RoK : Tandem)
Secondadry:
Doppleganger ~ New level 80 spell in RoK, long recast
Split Personality ~ AA choice that few raiders take
Touch of Empathy ~ AA choice that few raiders take
Sever Hate ~ AA choice that few raiders take
Prismatic Chaos (RoK : Prismatic Adornment ) ~ Short recast in combat buff, impractical to really use in this way
There are 4 quite easy choices, the 5th could be much debated, although imo once at level 80 it would be more practicale for it to be doppleganger due to every illusionist having this abilty.