PSA: Multi-kill limit.

[Sylkis]

I believe the reason why it might hit different mobs every time is because of how AOEs work in this game: The closer you are to whatever casts an AOE the faster you will be hit by it. A good way to observer this is in Titan, where you have lots of unavoidable going out (tumult) combined with lots of AOE healing from succor/medica/medica II. It's also the reason why if you precast a big hit too early you can still heal up some of the players.

Actually, that's just an animation. Try using an AoE heal then queue up an instant skill, the heal numbers will appear on everyone at the same time