It's pretty simple if you have a well-rehearsed raid leader who can shout specific instructions at each given stage of the dance. That's all Garrosh is; a long dance. You move in, you move out, you move to the side, you move in, you move out, etc, etc. So long as everyone can follow simple directions, it's a piece of cake.
That said, I don't think every endgame boss has to be able to be beaten by PUGs.
Choosing to quote you running with a 7/14HC group as a measure of Garrosh pugs success was a bad example to make the point. I think people with brains realise that all pugs aren't the same...
Sorry, I guess I expressed it badly. It was primarily a reaction to the "Don't try to PUG Garrosh," "PUGs can't progress," etc. threads. The point I'm trying to make is that some PUGs I've been in, even without doing any heroic bosses, have 1-shot or 2-shot Garrosh, and that I have indeed been able to progress beyond what my guild has done in some PUGs. Coordination and communication vary, a lot of the weight rests on the raid leader's shoulders, though they can delegate someone else to call certain things, etc. Even with poorer DPS and getting more EWC's, a group can still beat him if they don't tunnel. They need to handle adds properly and interrupt/attack the MC's. However, more DPS does make it significantly easier.