One huge advantage Wells has as part of a committee of RBs is that he's a respected Special Teams player IMO. Again, to be insurance on game day, you have to dress (45 men +1 QB) and it's huge if you are not a liability on ST.
If the Texans get a new RB (draft, or FA), will they dress 4 RBs on game day, or does somebody have to go?
I could see the Texans either:
a) getting another RB (draft or FA) and dressing either DD, or Hollings, along with Wells and new guy (this would address the situation identified by Vinny where DD is productive unless he is dinged (ie don't dress him), or perhaps you prefer to say DD isn't durable). Perhaps this would allow DD to return kicks; or
b) get another RB, but a low draft pick who is essentially a prospect, who makes the 53, but doesn't dress early in the season, or until there is an injury.