It is interesting that each of the FA signings addressed an acknowledged weakness, particularly with regard to the interior DL. In that regard, I give the FO for finally addressing specific needs. And, yet, it really didn't work out.
For the most part Dallas has used FA to plug holes rather than find that "one player away" from a championship. Yes, I know this isn't a hard and fast rule, but it is certainly the recent pattern. They have also targeted the player with past success that is either coming off an injury or is considered over the hill.
My takeaway is that their intent isn't bad, it has more to do with the execution of that plan. The talent evaluation.