Everything succumbed to the merciless auto-resolve. Maybe weighing is badly skewed or something. I don't know.
Auto-resolve weights are ridiculous. If you want to have fun, start a game as Empire and field a full stack of Any Lord + 19 Free Company Militia and only ever auto-resolve because that composition is pretty bad in regular battles. As long as your are not outnumbered, it's almost always a win if you auto-resolve.
They can be good to abuse if you are fighting a particularly tough battle... but that is weighted in your favor.
In Medieval 2 Total War, for example, Citadel (Essentially THREE wall Castles) weren't counted for battle weights, or at least barely mattered for the calculation, even though it is a very good way to lose a lot of units.
On the opposite spectrum you could also get Cannon Towers which were SO overwhelmingly powerful that you could win exclusively through those. So it was pretty much never in your favor to auto those (unless the enemy has them)
This game... is the same deal.
The Undead are probably the weirdest in that some of their garbage units seem to weigh the scales more than their actual provable strength, like zombies or skeletons.
While I "THINK" the group that is weighted wonky in a "weak" way is probably the Dwarves...
(Then again what a coincidence that those are polar opposites: Dwarves have amazing first tier units, and Undead have DREADFUL first tier units)