Ok, so I got into a fight with a troll who was going to absolutely wipe my donkey. Out of desperation, I used stoneskin on my champ (who's the tank) and then dropped that mud spell to slow his movement across the map.
Then, I began using Wither, over and over and over...as I had three champs that could cast it.
His attack dropped from 40s to 16, all the while while my champion nickel and dimed him down. I continued to cast wither to get him to zero (testing), and out of nowhere, the battle ended suddenly. The troll still had at least 25% of his hit points. Also, all of my champions (4 in the stack, and yes, the experience was almost non-existent) suddenly ported back to the nearest city, leaving my main sov and the army units left in the stack.
This brings up two things:
1) is stacking wither like this meant to happen? I actually like it, really, as it felt I had a viable strategy, but I do think that if it is intended, the mana cost should double every cast, or something. It needs to cost something to bring a troll from 40ish strength down into the teens lol.
2) Obviously, there is some bug upon doing this that causes the troll do die before hitting zero hit points and also my other champs being transported to a city from out in the field.