So, I snuck up with my sorcerer and just endlessly pegged the Bullette with Firebolt until it dies. My companions kept him in frozen combat status while I just slowly dwindled him down and killed him.
[sarcasm]
But... but.. but... you don't have to use it! Don't force your well functioning stealth system on everyone!
[/sarcasm]
Yeah, combat bubble should be wider and include everyone - stealthed or not. I think it is alright for character far away to be able to trek to the combat encounter though - it will be helpful in coop game, but even in singleplayer, I bet the only time you will have a chracter far far away, is when you loose him through toilet chain controls.