Your SP aren't bad and I have to agree: if Harden finally stays healthy you got your ace and a very good staff. They're good as a group, even with a questionable Harden but I expect big things from him.
Shields and Linebrink will give you some wins, but they will help you more with your ratios and Ks more than wins. I'd look to package Helton with one of your closers to acquire a stud just to hang on the safe side, then pickup Jackson.
Your team could use more speed but it isn't really necessary. Guys like MCab, Wells, and Holliday will chip in, along with a combined 60 or so from Roberts and Rollins; not enough to dominate but definately enough to compete.