Game is simple. You request an ability from another class that will get added to your tool kit, but it would have a corruption effect to it. A few examples to get the ball rolling:
I wish mages had warrior leap.
leaping causes your character to be momentarily stunned on impact.
I wish warriors could cast portal.
portal spell is automatically randomized on usage.
I wish mages had fade.
when used, one of your transmog pieces disappears for 24 hrs. Effect stacks.
So, for my official first request…
I wish mages had paladin freedom spell.
(next poster, please corrupt my wish and request an ability for another poster to corrupt your wished ability)
Pfft, I want the old vanilla trees back where you could go as much tank as you wanted and put in dps or utility. Magic damage and healing. Retribution and healing or healing with tanking. Affliction with pets. The skill trees we have now are very mathy and not very choice oriented.