SF has enough young skilled weapons with Gore, VD, and Bryant that they should manage as Alex Smith grows and Norv Turner does what he does best as an OC.
Houston has installed the denver system, bolstered their o-line, and added a legit #1 WR (they already had one in AJ). Unless Carr continues to have to throw off his backside every other play, they won't be near the worst.
And Cleveland, even without Bentley, still has off-season upgrade OT Schaffer, and the return of Edwards, KW2, and addition of Jurevicious should be enough to give them a decent offense.
Minnesota I think could compete for worst offense, pending how many game Tavarisis Jackson starts.