I actually think the Rebels will be a stronger team this year - if they perform to their potential they may even manage to get off the bottom of the table!
As others have mentioned, they have a very weak tight-five (probably even weaker than last year now that Sommerville is gone). Their loose-forward trio is actually pretty good (Saffy, Lipman, Delve) but they are really lacking depth behind this top trio. Their likely starting backline (9. Phipps, 10. Cipriani, 11. Vuna/Mitchell/Kingi, 12. O'Connor, 13. Mortlock, 14. Gerrard/L Mitchell/Kingi, 15. Beale) could be quite effective on attack if they are given some good ball to work with (a big if), but (as had already been mentioned) look very weak on defense. Cipriani and Vuna are shockingly poor defenders, and Mortlock's lack of pace is a big worry, especially as it look like he will be starting at 13 rather than 12 this season.