Doesn't the idea of opting into and then out of rage/defensive stance within a round seem hokey? I'd suggest only allowing one or the other in a given round to close this loophole.
Of course, I rage one round, wail away, deal with the AC issues before my next attack, and then wail away a second round only to end the rage before the end of that round. Basically, you could still do it every other round.
Ugh.