Our guild did it slightly differently. We had one ranged dps stay up top doing the puzzle with the offtank. The boss puts a debuff on the tank that stacks up and each stack is a 16% armor reduction so It can get rough on the healers rather quickly. After a successful firing of the puzzle we would switch tanks to get a refresh on that debuff. It takes a little bit of time for the tank to get back up to the puzzle but what we had the tanks do was pop a defensive cooldown (if needed) and run through the proximity mines, NOT the stun mines because that would be terrible. We didn't actually get the boss down because it was getting late. Our downfall was the stun mines, our healers were too often stunned for far too long. We called our certain mines that were in the way of the tank to be cleared but I like the idea of having the dps take out the mines once the boss has to many defensive stacks. That would've solved our problem. We will get him down this week!