Safeties often look bad, when they are trying to cover up and save somebody's mistake somewhere underneath......the position developed the name for a reason. You don't hear anyone saying the last line of defense should have been named "Risky" instead of "Safety".
The weak spot in a cover 2 shell, is the deep sideline. The play that everybody focuses on where he closed the space and made the leap and the ball went just over his hands for a completion? Not the right play to focus on for Obi's issues. That was just a fantastic offensive play. it happens in football, and inch or more here or there, and it's a fantastic defensive play, instead of fantastic offensive play. Nobody did anything wrong on that play, unless you want to single out the defensive front for not sacking the QB, or at least getting enough pressure to disrupt the throw.
That said, Obi needs to be disciplined this week, because he will be a target for the option offense we will face. He bites too hard, or makes the wrong reads, and we can get exploited. But he's not alone, the entire D, will need to do the same thing, it will just be more obvious, if he effs up.