Something is definitely wrong with some of these mobs. Check the combat log below. This lava beetle basically chained these spells until I died doing over 4500 damage. This excerpt alone shows some kind of weird behaviour since the beetle hit me with two spells AND melee at the exact same time.

I can vouch for this as well.

Sometimes mobs get cast happy and can actually spam out spells faster than they can melee. It's almost like they go into Frenzy... but with spells. If two happen to do it at the same time you may as well just kiss the ground.