For his career, Votto has hit .214/.318/.341 with 2 strikes. Compared to his 2013 line of .179/.311/.256, that's 85 points of slugging that have "gone missing" if you will.
A good part of that is his lower 2 strike BABIP (.310 this year, .352 career). Whether that is a function of a change in his approach or simple small-sample BABIP randomness can be debated. But it is undeniable that he has done less damage in deep counts this year than he has in prior years.
Don't get me wrong. In the big picture of what the Reds need to do to improve, Votto is among the last places you need to look. Despite the lull in slugging, he's still been enormously productive. But, beyond the unfortunately reality that it detracts from larger, more readily addressed issues, it does relatively little harm to recognize that we're not getting quite as much from him in the slugging the department as we had expected.