Some theorycraft changes to Sadhu that might make the class worth picking:
OOB: Remove from the game, replace with something like Snap from RO which allows you to move instantly to a selected location on a high cooldown.
Prakriti: Remove from the game.
Body Explosion: Replace with a skill that throws your spirit into a area for AoE damage and knockback.
Vashita: Make skill a toggle instead of a channel, aoe is around your character.
Possession: Make it un-cancellable by attacks again(yes it was a bug, but cmon)
Prana: Make it all stats instead of just int and str, no longer a channel, either instant or 1-2 sec cast with a reasonable buff duration, 2nd row.