Am I missing something that could make this build unplayable?

https://pastebin.com/FCyfb1qF

This build revolves around running around with reverse knockback cyclone, blowing things up with Molten Shell, triggered with reflected damage from Hiltless and Defy Pain. Transcendence is necessary, because otherwise, a pathetic ~7k phy hit from defy pain would only tickle the molten shell.

In PoB, this build is near-immortal with enough damage for end-game content. Super fast boss kill speed when you can get Vaal molten shell up. The only thing strong enough to kill it, is itself (or any other large phy hit while molten shell is down.)

But I have some concerns. Namely:

1. Is molten shell damage increased by the double damage modifier on crest?
2. Is molten shell damage increased by aspect of carnage (build assumes not, damage corrected with a modified gem.)
3. The helmet enchant increases the %protected HP all the way up to 100%/95%. Does that actually work, or is PoB wrong?
4. Does molten shell actually block reflected damage?

Lastly, any thoughts on how I could squeeze out some extra passive damage?