I would encourage you to try out the SM7 and maybe even a Senn 421. I think both do a good job mellowing the high end that ~I~ associate with a nasal voice. I own both and find that they are mellower in the nasal area.
While I do not own, and have never used a AT4050, I feel pretty confident that a 414 would not solve your problem.
I love my 414, but I picture that mic perfectly capturing the nasal sound.
I do not know the guy that you guys all hate, but working on singing technique should not be over looked. Please don't flame me... I have had to work on my vocal technique a bunch this year.