Also kinda the same issue, I was chased by lv 7 skeletons back to the town and I got up on the wall looking down at them. I could target them with all my spells accept teleport. Said Target out of sight again even though I could hit them with every other damage spell.
Oh then they came right through the gates, no stopping them. Wasted several guards who were just lv.5 Oh and btw.. The Drill Sargent in the training grounds outside of Aureus house. It says he is Level 3 but he is training lv. 4 legionairs. But when he fought he seemed to be tougher than lv.3
I love that battles like this can happen though. Just need to work out some of these bugs. I tried to use my Spider to lure the Skeletons into these fire creatures to fight each other but they seem to be part of the same faction and won't attack each other. I hope all monsters aren't part of the same faction and won't ever attack each other, or rather I hope the editor lets you assign monsters to different factions like in NWN you could do that.