The crab people armor has the highest defense values, just not much beyond that. The armor you get from the last promotion has awesome stats on it, but that's a little too late to be useful. Also the armor from the last level is great... again pretty late in the game. I used the barbarian set from canada until the last level.
Not much compares to the defense on the crab armor, especially not the barb set. I just like the increased damage from the barb set over defense. To destroy that boulder, you need to use the 4th (final) fart power.