If you don't view Perales, Clarke and Early as viable SP'ers in MLB for the future, I think you have to count all 3 as RP'ers.
2 Starters: Tolle & Valera
4-5 Pen: Perales, Clarke, Early, Sandlin and maybe Paez, Monegro, Mullins and farther away: maybe Delzine, Cason & Rivera move up.
I'm talking 1-5 years away. I have to think more than 3-4 pictehrs in our system will make an impact in the bigs. Hell, the widely panned DD farm gave us Bello, Houck, Crawford and some decent pen arms. (not all his guys but were in the farm when Bloom took over.)
I think you are being pessimistic. We've invested heavily in the farm through trades, higher drafting and signing bonuses and more IFA money to pitchers in the last 2 seasons, under Brez. Almost every trade involved us getting a pitching prospect, even the ones where we traded away pitching.