I know this hasn't gotten much discussion this season yet, but there has been a huge drop off in offensive production across the league.
.246/.319/.407 is the MLB average this year. Last year, it was .255/.324/.426. Ben 10 is currently at .255/.344/.418 for an OPS+ of 102, which is pretty much identical with his OPS+ of 101 last year.
There are also 2 very simple ways to make Ben10 a very productive player and hitter instead of an average one. The first is moving him to CF and given JBJ's struggles, that may happen sooner than later. The other is to simply platoon him. It's already been pointed out, but Ben10's career splits vs RHP is a very sexy .289/.364/.477 slash line in 735 PA. Hopefully he learns to hit lefties but right now he's basically a Trot Nixon who can play defense. That's not a bad floor. He also may not be the best base runner, but he is a good base stealer, although that may be an organization thing.
JBJ, OTOH, didn't really have much of a L/R split until this season. He only has 33 PA vs lefties this year, tho. Of course, he hasn't hit righties at all this season either.