My main class is CON too, and although I complained a lot about the MP cost changes when I read the patch notes (while I was still downloading), now that I've played for a while, I noticed..I get by with these kind of MP costs.
Maybe I always was careful with my MP management, I don't know, but I don't run out of MP as fast as I expected.
The only annoying part about it are the long pauses I need between fights to recover MP..that's why I think those changes were too drastic, but overall a good idea.