Let me say first off, the myth that you can't skill the bosses is just that, a myth. There are ways to deal with their stuns. If you take notice, the bosses "say" things on occasion. Now look at this screen shot.
When you see this, immediately stun him. This prevents him from stunning you. I believe Sacrifice also works if done in time. I haven't tested sleep yet, but it's a thought.
Edited by pdfisher, 06 August 2015 - 04:51 PM.