Even when the Warden's new sonic attack should hit multiple mobs at once, it only ever hits one of them

How to reproduce this:

1. Surround a 1x1 area with walls and put multiple mobs inside of it
2.  Spawn a Warden next to it (with no other distractions for it)
3. Hit the mobs to get the Warden to attack them
4. Warden has to use the sonic attack
5. It only hits one of the mobs

Edit; I had a thought: Other Wardens would probably need to be immune to the sonic attack