There was just too much pressure last year. Klentak's bullpen plan may have still worked in a normal season, and they certainly wouldn't have had to make the first trade they could so early in the season. It's just incredible that both of the better guys bombed so hard, and Hembree wasn't even as good as Hale.
Even as bad as the bullpen was, they could have made up those 1-2 games into the playoffs with another starting pitcher (particularly given all the doubleheaders).
In any case, it wasn't a terrible trade, because the Phillies' need was so great, and the price ultimately wasn't that high. But it would still rankle if Pivetta turns it around, and he surely has a better chance of doing so than Tom Eshelman or Jacob Waguespack.