Yup I had something similar except it was turn 31, with 3 skeletons.
On the skeleton point is the combat calculating correctly? They seem to be winning even when they are outpointed. I had a hunter with +60% (melee and the +20 bonus) and first strike in forest, up a hill get completely creamed. It wasn't a one off for the skeletons either. Other strange examples that repeat include a first strike scout with +20% in similar terrian got cuffed by a wandering lion. Conversely the enemy orcs can't seem to fight their way out of a rice pudding. Any ideas?
In my expierence, it moves until it finds a player then annihilates them then goes to sleep. I think it should arrive disgorge then move on. every game I've played someone has died before turn 50, goto worldbuilder and you see the dirge sitting next to the ruins.