All of those complaints should have been summarily dismissed, because the fact that the situation was self-inflicted meant that they had no merit; unfortunately, Bethesda chose to employ selective reading and only accounted for the 'I can't do this quest cause the giver is dead' part while ignoring the fact that the complainers were the ones who'd killed the quest-givers.
Yeah, I'm not a fan of the Companions line either, in no small part due to the fact that, unlike the TG or DB, you don't get to do side jobs between main missions to give yourself a sense of actually having worked your way up. Instead, they ram the whole line down your throat and then offer the side jobs, which is just silly on the face of it. That you don't get the option to join the Silver Hand instead doesn't help, especially considering that the fact they hate werewolves isn't necessarily a bad thing given some of the reasons why they might harbor said hatred.