Oh wow. Yeah, I was able to reproduce that warlock souls bug. For some reason the building is factoring it's own contribution to max souls but not actually increasing the maximum, thanks for finding that for me. Yeah, the incrementing difficulty doesn't progress high enough. Enemies gain HP with each wave. I just checked the math and it goes from 100HP at wave one to 108 at wave 20.
I've dedicated the past two months to learning how to properly procedurally generate isometric style tile-maps and my end goal for aesthetics was to have a starcraft1-esq feel to it. Having it compared to those maps is a huge complement.
It looks like one of your units wandered off and found a mask. The masks makes that specific unit stronger and he'll respawn automatically with a time penalty instead of die.
If it's okay with you, I'd like to post that screenshot on the game's page. Thanks so much for giving it another shot and all the feedback.