Yeah, the fact that the correlations are keyed to all teams rather than a correlation based on how those positions performed at each school means there is a potential for wide variation. Connelly claims his number account for things like returning DB tackles, #2 and #3 WR, and QB, but how could it do that effectively for any given team when all teams share the same position correlations? If Team 1 throws the ball around evenly to six guys and loses their #1, how is that comparable to a team that threw to their departing #1 60% of the time? How does his system account for a team like Georgia Tech? They will get dinged more if they change all their WRs rather than RBs. I bet their performance is affected less by changing WRs, which Connelly says is more important overall.
You note Locke, but Hager is another guy whose output could actually be worse than the guys behind him. Losing Wheeler is probably more harmful because we also lose Johnson, but in a vacuum just losing Wheeler might not be a bad thing. On offense, losing Watson could hurt, but it ignores the fact that Watson was a grad transfer (as was Anderson), so what if we get another one this summer? It also can't full account for the fact that Ingram would have likely been our leading rusher if he weren't hurt.