A few of us did this and having the enslaved junk tank the warlock guy did not work.  And it was tested over and over of them not working.  The hardest part of this fight is keeping that guy tanked so he doesn't kill anyone while having a mage or two who don't mess up the shield-stealing from the mage boss.

Finally we just had a warrior or bear tank the lock baddie and all went well.  FSE could do this easily with the numbers but it sounds like some people are happy where we currently are.