Yes, the Texans did play against better defenses in the second half/I agree with you somewhat on BOB, but DW4 shares his part in this too. So no it's not the main reason, it should be equally shared. BTW, how did the Texans go from being a decent offense to a crappy offense in the last month of the season? Could it be that they were playing better defenses that had DW4 confused, or did BOB become an idiot over the last 6 games of the season? I choose to think BOB was calling plays to protect DW4 from becoming a turnover machine. Or atleast I hope that's the case.
BOB has never been an idiot; just not good at scheming and designing an offense.