Where is it written in scripture that a power called "Unyeilding Stance" has to ROOT its possessor? It makes a little more sense in the Stone Armor set, but not that much. It sure is NOT standard comic fare that a Brick-type hero has to completely immobilize himself to resist status effects.
Why couldn't Unyeilding Stance just slow us? Or perhaps, if you are worried that Super Speed would obviate the slow effect, put a movement cap on US (like normal, non sprinting movement).
I will also agree that making a power like Invincibility, which depends on having a bunch of enemies around you, is inherently incompatible with knockback powers, and shows that someone did not think things through.
