Round table

Or maybe it was with another Vistan. In the 2nd screenshot, there was a single unit covering the gremlins, and a full stack was walking first, so it hit the ballista.

Well, that's what I called the AI's quirk. That is, theoretically, this can happen, but in practice, a full stack usually hits the gremlins. So, it's not wise to rely on this possibility in online games. The same applies to the 3rd screenshot.

By the way, someone pointed out that Aine also had a +1 strength breastplate. With that, the battle would have been won with good chances (if it were necessary).

I noticed the breastplate, but I didn't pass it on; she fought without it, simply because Anya is needed in the lower left corner - to collect money and take the crypt. Passing on the breastplate is something like upgrading gargoyles or golems - it's suitable for the task of taking it by any means, but it's not worth doing in a real game.