I tried it – the following inconveniences arose:
I'm just asking myself this question because, using this method, I still managed to win with your save, but I wasn't overjoyed because I assumed that the remaining army wouldn't be enough to destroy the enemy forces, but nevertheless, I'll say this:
in this case, it is, of course, about petrifying the dragons (it's reasonable – it's a must), but nevertheless, the Dark Knights and Vampires don't really interfere... ;) - this is always done by just one snake, which lures a group of vampires to itself in such a way that in the next turn they won't be able to reach the Liches (there will already be another one there :)), thereby
firstly: preventing the Liches from shooting
secondly: returning the Black Knights back (and also the skeletons and spirits, by the way)
5. "The best is the enemy of the good." I stopped worrying about minimizing losses after the first version of the battle (a triple paralysis happened to be available during a clean playthrough – it would be a sin not to use it). Time is precious, and besides, further development of events was possible even with this outcome, and the "extra" troops still wouldn't go anywhere – there are not many Free Guilds on the map.
Well, in your case, there was simply no such need :)