What's the deal with that ? Happen very often now and it's not lag related.
I even get the XP from killing it and is still standing shooting at me for 2-3 sec before the death animation start !!!!
It's often like that
You hit mob for 100 of damage (Last blow)
(Death music)
You received 500 xp
(Mob still standing and shooting)
Mob hit you for 25 of damage
(Mob Still standing and shooting)
Mob finnaly die