I actually don't think it's all that relevant in evaluating players in our defense tbh.
For example vs the run our LBs are often tasked w spilling blocks and so our safeties/Taron Johnson are going to have lower average depth of tackle vs their peers which is less a function of their quality of play than it is our scheme
Likewise Edmunds has a much deeper box than a traditional MLB, so average depth of tackle isn't going to necessarily reflect on his play either