This RB situation is tricky.
By all reports the Cowboys really like Dunbar and have no plans to cut him.
McFadden has looked good in limited action. Now isn't the time to cut him.
Is Randle really so bad in pass protection that the team is willing to cut him? Seems unlikely. And if you do cut Randle, do you replace him with a 30+ year old veteran who may be out of gas? I don't think so.
The Cowboys want to keep a fullback, so Clutts probably isn't going anywhere.
There won't be enough room on the final roster for 4 RBs and one FB.
Unless one of the three current RBs sustains a serious injury, I don't think that the Cowboys have seen enough wrong with what they have now to merit replacing one of their current top 3 with someone new.
Personally, I think the team is overvaluing Dunbar. He's a luxury that you can afford if you feel very good about your other 2 RBs. The Cowboys shouldn't feel great about Randle and McFadden at this point, so that third RB spot should be used by the team to churn for legitimate, viable solutions (instead of a change-of-pace).