I don't think RNG based jobs are a bad idea, we have 6 melees and only 1 has RNG elements, MNK.
RPR could be a good candidate since it has so little positionals.
DRK could have procs to make the filler more interesting.
Healers could benefit from it as well... What if their dots could proc a cooldown reduction, such as WHM's Assize getting lowered by 5 seconds? It's only my opinion but I believe Healers lacks reactive gameplay, which makes them very boring when the situation is under control.

I've tried WoW and something I like is a proc that would allow to use an Execution type GCD, that Execution would lower by few seconds a 2 min cooldown.
The only request I have is that the procs should be visible on the job gauge, I don't want to have my eyes glued to my hotbar to see which buttons is shining.