The entire draft is a crapshoot. Your logic basically implies that no draft that has ever taken place for any team should ever be criticized.
Specifically related to Dowling, this is a player that had a history of injuries. The Pats, for one, took him higher than they probably should have. For another, given his history, should have probably forseen that lingering and continuing injuries would be a problem in his pro career. It is what it is. They missed. They've also hit on a number of these. But if you're going to celebrate the number of players with similar pasts that they've hit on, you should also be allowed to criticize it when they miss.