Much as I'd love to see DD rack up 2000, it doesn't seem very likely and that is PERFECTLY FINE. If he finishes with 1200-1500, AJ's over 1000 yards receiving, and the Texans are piling up TDs and wins, none of us will really complain!
We haven't seen enough of Hollings to really KNOW. But I think it'll be easy for him to work into the lineup this year because the rest of the RB competition of last year is over.
My nightmare scenario, of course, is that Hollings' knee blows out again and DD has a year full of nagging injuries.