I dont agree PC. Truth is that if Hellickson and Buchholz pitch well they will only make 20 starts for the Phils because (hopefully) they will be traded. Add Kendrick and Saunders to this list, they are just on the team to showcase their skills so we can get prospects for them. I only hope for 1/2 a season from them, if we get a great deal more than they have by definition failed. The teams record, while certainly influenced by these guys, will be driven by the next group of players as they will get the majority of the PAs and Games Started.
I think the hope for .500 is in the next group of players. Nola, Eickhoff, Franco, Joseph, Herrera, Hernandez, Crawford and Rupp. These are the guys that must be successful this year for us to get to .500. Add in 1-2 others that are not currently considered "core", much as Hernandez and Rupp stepped forward last year and Herrera the year before. These are the players that are going to drive the team to failure or success in the short term, because they will be the ones getting 30+ starts and 600+ PAs.
To me the driving force that will make this team win or lose is not at the top as you have stated, but really in these middle guys that will drive wins or losses this season.