Let me start by saying that Issadora is extremely fun. She has good damage, can attack from a number of angles and do decent damage. Not to mention that Reactive Chains is probably one of the best anti-escape tools in the game.
But there are a lot of problems with Issadora, and a lot of her abilities need tweaking. But right now the biggest problem I see with her is this:

Here's a theoretical scenario: I'm at 70 Shields and I'm about to take a PuP ultimate, so I don't want to be out of my Forceball when the turn is over. I have 50 Energy and I ult.
Annnd I just lost 20 Energy.

The biggest problem I have with Issadora right now is that it's incredibly easy to effectively "waste" energy by ulting too early. This is especially annoying when you ult just to get knocked out of the forceball (let's face it 100 damage in a turn isn't that hard to take if ultimates are in play) and have to start from scratch because "XD You lost half your ultimate for no reason!"

I think Issadora should either retain energy if she can't add it to her shield (taking the previous example: I'd only use 30 energy to give myself 30 shielding, and I'd still have 20 energy left over) or should temporarily "overcharge" her shield past 100 when she ults, letting the extra shielding absorb some damage for the turn that she ults. (Similar to how healing someone past their health limit will negate any damage taken on the turn that they're healed, but not the proceeding turns.)