Noticed today that when leaving Plane of Disease zones you are dumped by the portal to exit Coliseum of Valor to go back to Planes of Magic. All the other zones seem to put you at their entrance.
Also, So Ro's Tower:The Obsidian Core also puts you back at PoM zone in. Oddly Monolith of Power doesn't, puts you back outside its portal as it should.
Just ran PoI:Masks of Marvelous and when we exited we were put at the PoM portal. Not sure it was doing this before?
I'm guessing this fell off your to-do list as it's still dumping us at zone out to Planes of Magic... so /BUMP!
It also depends on which exit you take - eg the one right near start of zone might be right, but the one that appears after final boss is killed might be wrong. If you have a scout you can try asking them to evac the group first, then using the one near the entrance.