I have NEVER arena'd in my life, but for theorycrafting sake. Your heals are 40 yards. Your attacks are 30 yards. Can you make a spread out macro to spread your guys out 12-15 yards away. It seems like AOEs are like 8-10 yards. It might clip 1-2 guys but that is all. It shouldn't take much time, should be able to do on a macro, you can probably not have to worry about facing issues if you use strafe moves. You might cover AOE fears, AOE stuns, AOE silences, etc. If you are just worried about one specific problem (bunched up), why not fix that problem? Or am I not thinking all this through?

Sorry, just trying to help.