This is actually an interesting thread. If you knew next year was going to be about the same at RB would you make a change? Our red zone efforts at running were better last season and we ran the ball well in spots and not so good in others. When you get spotty performances from the same two backs, it means that teams are putting more (or less) emphasis on stopping the run.
I disagree that teams did not stack the box last season. They did...in spots. There were also a lot of run blitzes against us late in the season that could transition to a pass rush quickly.
My biggest complaint about Julius Jones is that he is weak catching passes out of the backfield. For a back that likes the open field, this is a serious weakness and will keep him out of the "elite" back status unless he can improve.
That being said, I'm reluctant to make a change for the sake of change right now. Can we find someone better? Maybe, but not without using a high first day pick, and even that will be "iffy". Barring injury, our OL should be better this season and that should help production some.