Manastorm recursion mana cost + demon form glitch

Dunno if intended or not, but in a human form while using mana storm, say the base cost is 30 mana/s, and you use a spell costing 100 mana, the cost/s would be 60/s (makes sense, you use 100 mana, 30% is added to cost/s)
Problem : there is a recursion in the math, so with a single cast, it burns mana faster and faster, to the point manastorm is completely useless since it burns *the entire mana pool* with a single cast in ~3s since the 30% added to the cost/s of manastorm will be added to that 30% mana spent... you see where this is going
For people allergic to math :
cost 30/s with storm > use spell once > cost 60/s...150/s...700/s...2500/s without casting anything extra
It doesn't burn extra mana if you sustain the storm without casting, but goes out of control even if you burn 4 mana inside

Extra : as demon form, the added 30% to cost per second doesn't work, meaning it is possible to sustain it for eternity granted you have a mana regen above base cost/s

edit : vid of the questionable interaction : https://www.youtube.com/watch?v=9bQiTdx3F2s

I didn't notice that problem in human form but once I unlocked my demon form I did get the manastorm costing only about 5 mana a second

I also noticed after I got demon form I spent a ton of gold to respec to try out eldritch battery/mind over matter but it never converted my es to mana
Respec the point again and reloaded turned eldritch battery on again and. I just had zero es with no bonus mana
Was wearing grimtithe also if that makes a difference