I don't know if anyone has posted this but my static and I stumbled onto this a few nights ago.

We had trouble finding out where to stand to avoid double lightning when were down to the inner circle at the last phase. I noticed there is a big star shape in the center of the ring that has 12 points. Much like the hands to a clock. The points touch the outer ring when you are down to the last platform before the entire floor lights up. If you stand on the lines where they meet the edge of the ring your heat lightning won't overlap.

Example say the boss is being tanked at the line on the 12 o'clock. I was standing on the line at 10 o'clock and our sch was on the line at 9 o'clock. We both got targeted by heat lightning and we were just far apart that they didn't over lap.

Don't know if this has already been posted but it helped us out in the last phase when we were out of room to move.