Seranthony is a key cog, and he was obviously bad tonight (with help from Strahm). Soto has had a blowup game previously, too. Your bad bullpen outings can't be giving up 3 or 4 runs in an inning, it pretty much determines the game outcome in one inning. I don't know if the bullpen is overrated per se, or that bullpens in general have a really high variance from year to year and rating them is subject to lots of statistical variability.
On another note, I would DFA Pasche and start platooning Castellanos with Clemens when Harper returns. He's really a rally-killer right now.