Bad performance with heavy skill effects

Hi, since the patch i seem to be having bad performance in some heavy spell effects, mainly fire nova mine (my build atm) im using it with minefield. And between 3-6 mines I dont see any problem (even with allot of mobs/ground effects and skill effects) but at 9/+ from 100/120fps i go to 10-20fps during animation (even without mobs around). I mean before the patch i was dropping some frames too, but not that low.

My specs:
CPU: i5.5200u
Ram: 8G
GPU: Nvidia GeForce 940m

While this isnt a top tier laptop, this isnt that bad :s