So I think Doom of the North is my least favorite instance I have done. I've been soloing all of the epics and haven't had a single problem. In fact, I once even said that instances were too easy with the inspiration buff. I take that back. The first time I tried it, I spent a very long time going through Tham Something-that-I-can't-think-of-right-now. Didn't really have any problems. And then suddenly I find myself in a room where the angmarims just keep coming and coming and coming. And I die. So I tried again. Same thing. And then the third time, I get to that spot and I do just fine. I beat them all.
But then this wonderful little bug happens and my captain ends up stuck in combat mode. And I end up having to exit out of the instance because it wouldn't let me go on any further.
I think I died a little inside...
And I still have to beat the darn thing!