You might not be aware, but the speed sigil actually boosts all of your primary resource recovery. If you are having trouble upstairs managing resources, that would be my first suggestion. I would also strongly consider using a tri pot when you go upstairs. If you are running out of stam, you are either blocking, rolling, or sprinting too much. Never chase the shield, always go the opposite direction. Also, try to only block or roll his heavy attack. I find rolling to be the preferred method, but make sure you are not perma blocking in any way.

My method generally goes as follows once I am upstairs. Immediately start to DPS crystal to your left. As he charges his skull, avoid the red cicrles and dodge roll, then continue DPSing until the wall forms. You should be able to kill the cyrstal by then, but if not, move counter clockwise to the wall, and try to keep DPSing what ever crystal is closest. As a stam toon, its really important to get your ground dots on them as you might not be able to stay in melee while moving with the wall.

Once the wall explodes, you are going to have to dodge 2 skulls every time. Again, just stay on whatever crystal is closest and dodge roll when you see him charge his heavy skull attack. You have a fair amount of flexibility on the timing. Then repeat. If you get to a third wall, my advice is drop down and just kill the guard. The upstairs wont reset the health of the crystals but it will reset the timing.

The big thing here is to not get caught by the AOE or heavy attack. If you have to start breaking free, its probably over. Also, nothing says the cyrstals have to be killed in order. Just make sure you are good with DOTS and that you are always DPSing something.

You arent alone on this. This is the hardest fight in the arena out of the gate. It does become much easier once you get the timing down.