Team looks solid.
I'll start at the top. Stafford benefits from this format with the slightly increase points per passing yards (.05 per vs .04 per) and I believe his passing TD numbers will come up from last year to take advantage of the 6 points per TD.
I'm a bit concerned about your RB depth. Rice should be steady, Miller has a great situation and should run away with the job but I always get a bit concerned with early round backs who haven't done it before, and DWill should be flex-able for at least 6 weeks but than that situation could become murky again. I like Woodhead as a sneaky PPR play who should be able to pick up the RB slack should a starter falter but hopefully it doesn't come to that. At WR Marshall is certainly a stud. Behind him you have a decent corps. You don't have many high volume receivers after Marshall but the guys you have are RZ targets or burners so with TDs will come value. Whatever issues with RB or WR I just mentioned get remedied by the presence of Jimmy Graham. He should be a PPR stud and worth the second round pick.
Some other roster comments: I agree with your plan to not roster a 2nd QB or TE, especially with Stafford and Graham on your roster. Those spots are certainly better spent on WR/RB fliers.