The two Keepers outside Thorim’s area (ie. arena/gauntlet boss) can be positioned like shown below. This gives you more time to kill the Sphere they pass to each other.
Healers have good line-of-sight to both tanks by standing on the edge of the steps.
The tank on the lower platform needs to stand on the position shown to remain in range and not have them gain the +damage anxiety buff.
We didn’t try this on the platform they start at, instead I moved mine all the way back to the previous platform, just to eliminate the risk of accidentally pulling the two guys patrolling Thorim’s corridor.