The current arena really, really doesn't fit the boss battles scene. With a lot of players it seems almost crowded and or backed up.
There's nowhere for the boss to actually go without getting thrown around by explosives, and players who are late to the battle can't do a thing because everyone's in the way.
As the boss classes are set up, they're virtually not threatening at all in this map. Maybe give the boss classes all something to discourage getting in melee range of it, because right now it's just ridiculous.