If you guys see something attacking the boss, can you target the thing that's attacking it and then target the boss itself through that?

I know it's not exactly a great solution to the problem, but at least you can get an idea of what the monster is doing, and also attack it and participate.

I don't have the PS3 version myself, so I don't know how applicable this is, but in the PC version you can target your target's target through the UI. Wondering if that is possible on the PS3 version to at least be able to participate. It might not be possible simply because the mob doesn't exist according to your game, just throwing out an idea.