I understand your point in principle, and I generally agree with you, but I don't believe that it falls "squarely" on the shoulders of Beckett and Lackey. I mean alot of our bullpen sucked on its own, regardless of who the starter was. I mean when a reliever serves up a 400 foot bomb, that really isn't on the starting pitcher. It's not like the relievers ability to get batters out is different.
Sure, our bullpen was overused, and our bullpen sucked, and Beckett and Lackey weren't very good either, but that doesn't mean that all 3 are directly correlated and direct causes of one another. I mean sure, I agree with you that Beckett and Lackey are somewhat to blame for bullpen struggles (as would Dice-K in all of his 5+ inning starts) but at the same time, you have to blame the bullpens themselves (as well as management) for sucking so bad. I doubt that last years bullpen could perform with a good starter, let alone a bad one.
If having a few bad (or underperforming) starters is enough to derail our bullpen, then we should stop using such inconsistent relievers and get ones that perform well even with bad starters.