I ran into the same thing. Now that the harpies are more mobile, they can get close enough that they get lured in. I'm actually surprised some of the druids weren't pulled as well. They should tone down the harpies' flying around a little. In my case, all of my characters were down at the bottom near the water. Yet the harpies decided to all fly up to the very top of the cliff. I can understand getting to the high ground, but at that point they couldn't even pelt me with their ranged attack.