IIRC, their ZIPS projection piece on the Tigers after the winter absolutely hated the Tigers pen. I didn't read all 30 teams, but their combined value has to be lower than most other BPs.
As you suggest, this is a function of having young and relatively inexperienced talent potentially in high leverage roles. Just as we wish Tork/Greene successful seasons that involve chasing AL ROY (which, if happens, in all likelihood means they are much better than 74-88), we don't know that until we see them in the majors. Not to mention the starters and young relievers who (outside of ERod) are all still trying to prove themselves.
More questions than answers, but they have a lot of promise. I still feel pretty good going into next year.