I always though Brother Mouzone was on the same kind of 'level' as Omar. They didn't quite fit, like two super beings wedged into the real world. They even teamed up! Which isn't to say I didn't enjoy the crap out of it.
I don't buy it that Walt poisoned the kid, if anything Gus got the berries from Walt's back yard. But more than likely it was just a screw for the audience to go crazy over until the final season begins.
Walla Walla Bing Bang.