Actually I agree with you on that - I think being able to convert BYSSEPS probably gives your strategy the edge. I actually COULD have used EM for lots of greenblood, as I had barely touched any of my bloodpools (especially not the ones at the edge of the courtyard). I guess I just never considered how strong corrosion actually is, because in VGT this isn't an option. As for using spare piety to get more CP, the problem I have is that there are only a few gods that you can really afford to lose piety with - Taurog, Mystera, Binlor, and maybe Dracul if you have leftovers after Consensus. With that in mind, Mystera is pretty random and Binlor will only allow you to lose 10 - so most of your losses will have to come from Taurog. Taurog before Binlor means that you can't use the sparkles you haven't opened up with ENDISWAL yet, so unless you got very lucky with magic monster spawns I can't really see how you're able to get 200 CP... maybe with EM in the endgame after Plantation, but you're sacrificing corrosion stacks for that.
I've scouted a couple of EE Vicious but haven't seriously tried any of them yet. I think I'll probably try for Troll Lab first - I just unlocked it and it looks pretty interesting. Since all the enemies have fast regen, it looks like it favors damage spiking classes, which happen to be my favorite to play. Flooded Foundry with a parched Thief looks kind of difficult. I don't really understand how you can navigate this dungeon without something to break walls, because the amount of core stones you get really isn't enough to traverse the dungeon properly.