On boss 2 (Helix), if you stand underneath the logs facing away from where the boss is standing originally, it seems that you do not get hit by the thrown bombs. In addition, since you are standing under the log, when the bomb planted on your chest explodes, you just go up to the log. This turns the fight into a basic tank & spank.

I haven't tried boss 3 yet because as soon as I saw 'vehicle' I exited the instance .