Icestorm FPS Issue

Hello,
I did a Video on this topic if you rather want to watch this.

So my issue: I normally have 160-200 FPS in PoE but I would like to run a build of scorching Ray + Cast while Channeling + Icestorm. But unfortunately this reduces my FPS to ~50. This is not unplayable (I know that) but really inconvenient to play when 75% of your fps are just vanished just from this skill combo.
Additionally: none of my RAM, GPU or CPU are at its limits. Idling my GPU is at ~75% and CPU at ~35% (over all cores). When channeling the spell my CPU usage goes to ~45% and my GPU usage actually drops to ~50%. Since I run 16GB DDR4-3200 RAM I just assume this will not be the problem (I actually did not monitor this, my bad). My other Hardware is this:
Mainboard: Asus B350-Plus
RAM: 16 GB DDR4-3200 G.Skill Trident-Z
CPU: Ryzen 7 1700 @3,65Ghz
Graphics Cards: Asus GTX1070 DUAL

I am just writing this to raise awareness to this problem because I think the skill is awesome but kind of unplayable with this performance and there seems to be no good reason why it is the way it is. I also notice while searching the forums for other reports that this combo of spells had crashing issues in the past and maybe this is somehow related.

Thanks for reading.