I guess dmg is not that great but he can manage the combo mobs with in 3-4 sec rotations. His gear just making the move and letting kill them that fast, he has more than 1100 AP and using demi human. So his class is good and fast clearing combo and has big dmg cuz of new AP from nodes and new gears. I guess most of the classes can kill that fast with his AP but can't clear every single pack that fast cuz of CD issue
If he has Jojo pet then yeah he doesn't need to worry since that pet has a passive of extra range to get loot, it can get your loot from the other pack while you are at the next