Maybe. But maybe he would have tried it for like five seconds but then given up on it because he likes being angry and evil and doing stuff that makes him more calm just irritates him because he would much rather be doing angry evil in the wizarding world.
Oh yeah! Good point. Dumbledore did need Snape. Snape was such a complex character, especially compared to the moustache twirling villainy of Voldemort. I mean I do love the Harry Potter world but I have to admit that he was a one dimensional character. I half expected Voldemort to tie Harry Potter down on some train tracks!