LBs are supposed to hit gaps to blow up the running game. -Which is why I said the safety blitzes are only a partial explanation for the lack of LB blitzes. Ideally a hybrid safety/linebacker (Francisco, KVN etc) roams to provide either coverage or blitzing based on how the OL picked up the blocks. Bronco has no speed at linebacker and so he's been forced to invent safety blitzes and put undersized DEs on the edge to try and cut down throwing lanes.