The Blues are in a unique situation. They have a lot of young defensive talent that is barely starting to become NHL ready. Cole has played for a short period of time, same with Nikitin (who I think is forgotten). Nikitin has looked VERY good in his most recent call up and seems to be ready now, hence Strachan being sent down. Yet they still have more in the pipeline including Cundari and Junland.
They have their first set of forwards that came in with Oshie, Perron, and Berglund. Berglund is still trying to find his way, but he looks so dominating at times it's hard to believe he won't figure it out to be consistent in this league. Oshie is what he is, and willl be a Blue for a long time. Perron is the most interesting one to me. Sometimes he looks like he could be a PPG player in this league, and other times like a good second liner. He has world class skill with the puck, but often tries to do too much. Personally, I still think he will be the best offensive player out of their young forwards provided he stops getting headaches sometime soon. Then you have the next wave of forwards in McRae (who looked very capable when he was called up), Tarasenko, and Schwartz. I wouldn't mind seeing McRae back in Peoria to start next year since Tarasenko will most likely make the roster out of camp. Yes, I expect him to contribute right away somewhat at the level of Seguin since I figure his minutes will be limited to third line duties to start. Schwartz is probably still a year or two away, but seems to have some very good upside. The future is bright for the Blues offense.
Then you have Jake Allen and Ben Bishop. I would imagine that Bishop is the Blues back up next year and Allen takes over full starting duties in Peoria. Allen will probably be in Peoria the next year, too. Then you have Halak's last year of his contract and you decide whether Bishop and/or Allen are capable of handling the goaltending load for the year. Personally, I expect Allen to take over the duties after Halak's contract is up, but either way for the first time in a long time the Blues aren't hurting in the goaltending department.
I would say the Blues prospect pool is right where it should be. Definitely deserving of top-5 in the NHL at the moment. However, things can change but it looks good from where I'm sitting.