Self-cast rolling magma with 300% more AoE [Prototype / EXPENSIVE]

I found a crazy crucible tree on a Annihilating Light and wanted to make a build around it.
Also the budget for this is like ~80 divine not counting mageblood

Here is a video I made for it.
DISCLAIMER: I am not saying this build is good. It's currently lacking a lot of things because I suck at making builds, but it is really fun to play so far.
It really needs some defenses but my softcore brain can't figure that part out.
With that out of the way, here's the video

https://www.youtube.com/watch?v=D1xUTo5Lg1I

This is the PoB

https://pobb.in/M7kh1KyVLysV

Mechanics
I am self-cast rolling magma with the goal of stacking power charges for even more AoE/damage.
Take all powercharge nodes on tree, and make things go boom.
Omniscience for penetration/resistances
Diallas for huge gem levels, rolling magma currently level 30 without any +level investment besides dialla.
Defenses are: Kill them before they kill you (which is pretty easy to do since you cover the entire screen in eye-cancer)

HELP
If anyone has any great ideas for making the build more tanky without cutting too much damage that would be great.
I'm worried if I lose too much damage I'll lose my biggest defensive layer, which is my offense