One thing about the bubble is people use it wrong in PvP. If you pop a bubble for shelter to protect you...your doing it wrong! When you get your super, just about everyone will have theirs also. I found it to be more successful to pop a WoL bubble in an inconspicuous area and run out to the area enemies are and then loop back to 're-up the WoL. Sitting in that bubble for protection is a bad move unless your playing PVE. Of course this is my own opinion and I'm sure real good defenders (I'm not one) can merc you with whatever they use. As far as it being unbreakable....I think other supers should be the only way to take it down, and most do, so all in all I think defender is in a good place.