I am the healer for the back 2 tanks in the 4 horsemen fight. I was dieing a lot while trying to not let my tanks die during the switch... they were a bit undergeared.
I found out that if you stand at the top of the stairs on the center platform you can avoid getting the marks and also avoid the void zones. You must make sure you are out of line of sight of the 2 bosses or else you will still get marks.
The tanks also must stand on opposite sides of the teleporter in the back out of range of the opposite boss but still in your line of sight. When it is time to switch they run to each others spot at the same time. They get in range quick enough that the boss does not kill the raid.
Image showing where to stand.
This makes healing the back a whole lot easier... enjoy![]()