There is a lot of variability in the Saints offense right now.
The Saints had two backs catch 70+ passes last year, not one.
We've seen Ingram run, we know what he can and cannot do. I will give you an example: the @ Carolina game. Ingram had a very nifty breakaway run down the sideline and then cutting back towards the middle; somewhat reminiscent of Ivory actually, but the difference was he was tackled from behind before he got to the goal line. The Saints settled for 3, lost the game, lost the division, lost the bye, had to play on the road twice, etc. Small things matter.
It's not just that, Ingram fumbled vs Seattle, and it cost 7 and that stung. Ingram had a better ypc in that game but Robinson ran better and looked like he had a better shot at breaking away. Just an observation, but I think Khiry brings big play ability that Ingram lacks. IIRC the Saints' longest TD run all year was under 10 yards, maybe 7 yards (someone told me this, so I haven't checked my facts but it sounds right, believable anyway...).
Pierre: he has always had the vision, but he just seems to be going down a little easier, more quickly, a step is all it takes, plus he missed the playoffs again. And the screen did not develop like it used to and the same goes for Sproles for that matter.
Cadet: I don't see him becoming the "new Sproles." He dropped his one big specialized screen play in the SEA game, it was a huge drop, very well set up. Here's one thing he can do: if you saw the Philly game, Sproles has a sideline streak (or sluggo) route and in that game Brees overthrew him though he was wide open. I know for a fact that Cadet practices that play over and over with Brees. I don't think Cadet is anything special on ST and he's not a great runner. I don't see him ever being able to do what Sproles does.
I don't know where that second set of 70 receptions go, it may stay with the RBs (and yes as a matter of fact I think Robinson can catch and run with the ball very well), or it may get spread out to a new set of WRs, remains to be seen, but I do believe things are changing.