Pitching wins and losses are less than meaningless.
Depends.
Show me a guy who takes a quality start into the 7th, and then the pen blows it, I agree. But show me a guy who is constantly pitching behind in a game, and then loses, and it's a telling stat.
An example to back up your statement is Clayton Kershaw: Has a great year, Cy Young 'n all, then gets beat in the playoffs routinely.
And don't forget he basically lost the All-Star game this year.