-10 enemy or 15 % light skill thanks for explain

-10 enemy.

Because:
Low res mobs dies instantly.
Infinity is like 1/5 effect vs immunes, so would typical lower res from like 1xx to like 80. Then theese -res badboys comes in and handle that further down.

I think the current patches infinity is still nerfed to 1/5 effect after monster is sundered, im pretty sure i have seen people writing that a while back.