The theory behind NOT having the ranged handle the mechanic is if the fountain spawns next to the boss that's 6-7 players in a very small area, meaning people will get hit by pinions they would otherwise not have to.

We move the boss and do OT (3 stacks) -> melee (2) -> melee (2) -> healer (1). Tank moves after Revelation just for safety, which means we lose a little OT dps (a few GCD at most) but the DPS check is very lax at that point. Otherwise it has no negative effect on our overall DPS since the boss is positioned in such a way that you can keep getting both rear and flank positionals from inside the fountain.

Works just fine for us, but I know plenty of groups that don't move the boss and have ranged deal with the fountain. Do what works for your group.