Adrian Peterson could walk into camp and be third string, you can make 1000 excuses. We saw Daz get more carries than Brown and Irons and we know why. ...
Yes, we know why. The reason is that Daz consistently graded out better than Irons or Brown. As you said, videotape does not lie. The best back should get the most carries, and that's the what the coaches do, but they also try to get some carries in for the backs of the future.
Yes, if Adrian Petersen walked into camp, he'd have to earn a starting position, but that's exactly as it should be. No one should be gifted a spot without earning it. Could Petersen earn one? Absolutely. Can Irons earn one? I believe he can, but it still remains to be seen. Based on his play so far he has earned more time, but he certainly hasn't earned a starting spot.
There's clearly no other running back on the roster with Iron's potential for a huge huge season.
Dorian Brown is another outstanding back, don't kid yourself. On the recruiting forum I rated Irons as the best back that Solich has recruited at Ohio, but prior to Irons, that honor belonged to Brown.
If the offensive line gels, Ohio's running backs are are going to have a very good season because all of them are good.