Ugh, it appears I have played myself into a corner in this game. I was playing as a liberal reformist kind of ruler, which resonated well with the elves and lizards and sometimes even with the imps, but the undead hated practically all my decisions... which would have been okay, since I really disliked the stupid religious fanatics, but then Act 3 came around with its ridiculously huge number of invasion forces and suddenly I found myself losing the war even though I had everything researched and almost 900 gold in my treasury because every time you piss off the undead the gods "curse you", which means a -2% autoresolve chance, and at this point it added up to something like 20%, which combined with the occasional negative support maluses meant I often lost half my defending forces even when they outnumbered the invading forces three to one, and unlike those guys I couldn't churn out thirty units a turn to replace them, so I was beaten into oblivion in ten turns. Not fun. -.-
Really, the way the game takes away all the player's units and resources at the end of each act is just artificial difficulty, and combined with the issues of the autoresolve system it's just sadistic.
That said, I think I will go ahead and fire up my copy of Cheat Engine and see if I can hack it so that I can play all the battles in RTS mode. Wish me luck.