Took a few more runs than I had hoped, I was set to win on attempt 2. But just never got my 4th Strongbowmen ever, so was stuck with Rare emblems in inventory and nothing to put them on. Which made me lose to the boss. Then I had a T0 Fire Mage spam run where the boss lived with 1 pixel of health. But just standard T2 Footman + T2 Cleric + T2 Strongbowmen, all with below average mutation luck, got there in the end.
There appears to be some kind of either memory leak, or just very unoptimized code going on in combat as well. I don't think it's reasonable for this game to push my 7600x to 70-80% utilization and just sit there for a lot of battles. Really this kind of game shouldn't ever push it past like 20-30% if that. If I had to guess, it's probably something about how damage numbers are handled, as it seems to be worse when you have something like thorns or swordmen. But it's almost always pretty bad.