The second boss in Mechanar and the party are quite a bit faster then the Fire Elementals.
If the party is split (not an issue for boxers) then fire is all over the place.
With everyone together, it doesn't matter who the fire guys chase, just make a slow big circle around the room.

Quite a few people will clear Parthenon first.
And once he's dead, you can kite the fire lady down that hallway too.