FWIW, I think this is a schematic problem.
Our offense is often referred to as a conventional pro-set offense or a multiple offense, but these labels are not totally accurate. What we actually run is a one-back offense with multiple sets. The sets, formations and looks we show actually are closer to what you'd see from a traditional one-back spread passing offense than the pro-set offense. The running game is similar to the old Joe Gibbs/Washington Redskins power offense with its single-back sets and zone blocking schemes.
One of the best things about a one-back power offense is that - when properly executed - it allows you to run the football effectively against stacked defensive fronts. Each blocker occupies a zone, and even against overloaded fronts there tends to be a double-teamed defender or two and the tailback simply has to read the correct seam and hit it hard. This is why we've been effective running the football in the past, even against stacked boxes. It helps to have guys like Ingram and Richardson back there who tend to break a lot of tackles, as well.
What's changed this season? Opposing defensive coordinators aren't "stacking the box" anymore, at least not in the conventional sense. They're utilizing run blitzes. This is how you beat a one-back rushing offense. It's a numbers/speed game, rather than a size/brute force game. One of the problems with a one-back set is that you don't always have a fullback or a lead blocker. If the opposing defense puts a cornerback close to the line of scrimmage with the intent of rushing the tailback, and the tailback gets a handoff 4-5 yards deep with no lead blocker, that's a losing battle for the offense every time. The defensive back has the speed to blow past the tackles and tight ends. Even if the DB doesn't tackle the tailback outright, he's slowed the play down considerably.
A good defensive scheme will run blitz and squat on the short passing routes against us, which is exactly what South Carolina did.
How do we exploit this? As others have said, you've got to throw downfield. It's similar to the stacked box principle. The opposing coordinator has to respect the downfield passing game. Last season, we hit enough deep play action throws to keep the defense moderately honest. We haven't done enough of that this season, and we're seeing all these run blitzes as a result.