You're not the only one. I've said it makes more sense to spend some more money instead of trading prospects when the system has just recovered from the Marlins and Mets trades. Nolin and Graveman weren't high ceiling guys, but they provided starting pitching depth for the MLB team and could've ended up as relievers as well. I hated to see Barreto go, but I can see how a prospect like him needed to be included in the deal. This was by no means a fleecing, IMO, as I think Oakland got valuable starting pitching depth plus a good 3b in Lawrie with some nice upside and still just 25.
No doubt the farm took a hit, especially with Barreto gone. On the other hand, with a full season from guys like Hoffman, Pentecost, SRF, Osuna and Clinton Hollon, the system should get a boost next year.
We'll see what happens.