There are tons of horror stories about knockoff wheels. I agree that they are form over function, but they still must meet minimum standards or else they would be sold under 'for offroad use only' status. I bet you all those broken wheels had been raced, or hot a massive pothole or something like that.
Wheels don't just break because your car is too heavy for them. Even a steel wheel will get messed up from running into a curb or pothole. The difference between a steel wheel and an aluminum knockoff is that steel bends but cast aluminum breaks due to small imperfections. Knockoffs work great for a road car and look good too, thats about it.
I agree that, for caliper clearance, offset doesn't play as much of a role as spoke design. Having a smaller offset will get you as much room as possible though.