I have an ability that has a stun effect.
If I cast the ability on a mob, the stun works.
If I cast the ability on a player, the stun works.
If a mob casts the ability on a player, the stun doesn't work.
There is a bug with friendly AoE targeted abilities. these do not to any healing or damage to targets in range, instead all of the damage goes to the target that is currently selected.