I think your assessment about having good starters and weak depth is spot on. You can improve your depth on the waiver wire if you pay close attention early in the season.
Some specific thoughts:
-MJD is obviously a big risk, but I have to think he will work his way back eventually. He did lead the league in rushing last year. The holdout putting him behind is a worry though.
-I cannot believe you did not handcuff MJD with Jennings!
-Sjax will benefit from Jeff Fischer, who loves to run his primary ball carrier often (see Eddie George and Chris Johnson for example).
-I think Trent Richardson is a great pick, as he will get a lot of touches in Cleveland, as he is obviously their biggest (only) weapon on offense.
-Marshall and Jennings will be consistent producers at WR for you. Jennings is Mr. Consistency himself. Marshall is in a great spot with his buddy Cutler. Nice picks. You can confidently start both of them every weak.
-Gonzo is starting to slow down, but I cannot fault you too much for going with old reliable here. I might try to add a young backup with upside if I were you. Maybe the black unicorn (Martellus Bennett).
-Manning is a big risk. I would feel better about your QB if your backup was anybody but Carson Palmer, who I really think is finished.
Here is my team, if you wouldn't mind offering some feedback, I would appreciate it: viewtopic.php?t=518441