6’4” and 220 is good for some tasks, but not always good for others. Do we see many 6’4” 220 DBs? Or RBs? Or slot receivers? Think of how often an OLineman pulls, heads down field, looks for someone in the secondary and ends up hitting no one because they couldn’t close the distant and keep the defender in front of them. Depending on the situation, defenders can be told to never run around a block. The idea being if you do run around it, you allow the blocker to not just take you out of the play, but another player as well. Those DBs are not in that situation. Avoid the block, and get to that receiver, that's their mindset.
I do agree with you that if our guys are not up to blocking, they need to be rotated out more. Bullock blocks, primarily because he's done it since he was in middle school. He has that mental attitude, and really good technique. Coleman missed horribly on some blocks last year, until the light went off and then he became pretty darn good. I don't know what our top two have done over the course of their careers, but apparently they haven't got it down yet, and time is running out because we need to be able to execute that play.