Assuming this is a 12-team league...?
To start with, you've got a bunch of guys on your bench that you could cut (Polanco thru Feliz, except maybe Bradley) if a better option comes along thru a trade or the WW.
I like your SPs a lot, although I'd ideally want one more guy between Halladay and Davis. But if 2 of the 4 from Davis/Perez/Liriano/Kazmir come thru with a good season you're gonna be in good shape there. You do need to add another closer, though.
As far as cats go, you're right about needing SBs but it's not a huge issue at this point of the season. I personally have no faith that Wells is gonna have a very big season, so if he was on my squad I'd wait for a few big games and look to trade. I could be wrong, though... And your OF is a little thin with Wells and the Lane/Bradley combo, so I wouldn't trade him away for a different position.
Not a bad team overall IMO. If you're patient and make good moves you'll be in the running I think...