It's also worth noting that the goalies that were drafted last year are younger than Lindberg, so they still help fill the pipeline going forward.
Just to use this as an example scenario (not saying this is realistic, for a variety of reasons): DeSmith's contract ends after this current season. It's not out of question that he'd expect a raise on his current cap hit of 1.25M. In the ideal circumstance, one of Lindberg or D'Orio replace DeSmith, with the other remaining as the starter in WB/S. Blomqvist and Clang then can either come over and backup in WB/S or start in Wheeling, or else the Pens can loan them out to their European teams to continue to develop as starters overseas. This is not a bad situation to be in with goalies. If you're lucky, one of them proves to be good enough to be an NHL player. Chances are, most of them never see more than a few games in the NHL. Goalies are voodoo, so having a steady pipeline of prospects that gives you time to see which ones stick is necessary.
I mean, in 2011, the Pens drafted Murray and Maguire in the 3rd and 4th rounds, then drafted Jarry in the 2nd round the next year.
Oh, and then they drafted Gustavsson in 2016.
You never know how things are going to work out in the long run. You don't want to have too many goaltenders ready to be pro at the same time, due to lack of spots, but that's not really the case here. 5 goalies on NHL contracts spread between the NHL, AHL and ECHL is perfectly reasonable.