Like I said, my system might be different, and I acknowledged that I may have been biased towards positivity. But in this example, sometimes the opposing team is just going to make good plays. Joe's first read is run, which he followed... it was a great ball-fake by Pitt's QB, and was called at the perfect time, to the perfect side of the field. If anything, the guy who would earn a negative on this play is whoever the DE and/or OLB was, because they would have contain responsibilities, NOT Joe.
Here's where the negative bias comes in, IMO. You say he "bounced off," I say that he escaped the block and was in position for the gang tackle.
Also, your example is bad because I graded him negatively on the one blitz where he did get stonewalled.