I fired up a game to give it another go.
The auto-resolve needs some work.
I had a mid game stack fight two white spider groups. The power ratings indicated that my stack was much tougher. I hypnotized one, and inflicted about 50% damage on the other.
I decided to auto-resolve. My entire stack died. I could understand one or two of my weaker units dying, but the entire stack of mid game units? It shouldn't have happened.
Sorry, I don't have a save game file.