On the one hand, it's only been two week and we have two rookie offensive linemen playing. The Running game may take time.
On the other hand, I have seen no signs that the Cowboys have a running game they can depend on. I won't blame the RBs alone, but I am pretty sure Deuce Vaughn is not going to do anything for the Cowboys. I am also fairly certain Zeke isn't threatening any defenses either. I think we can deduce both of those things from what we have already seen, and from last season too.
Rico Dowdle is a JAGs. He doesn't have great vision, he is a guy who ploys into the hole with reckless abandon and bulls his way to ad most an 8 yard gain.
Maye week 3 isn;t the week to make any changes, but if the running game does not improve this week, then I definitely think week 4 is the time to test Cook to see if he can do better I am pretty sure he couldn't do worse.