One thing I've always thought interesting about Phoenix...
Marvel says that Phoenix can generate any form of energy in any conceivable amount. I would think that that would include magical energy as well. And thinking of PF in terms of being the wellspring of all of creation, that would include magical entities indigenous to the 616 dimension as well.
I think it's an aspect that Marvel should explore a little more, since Jean and Rachel rely almost exclusively on TP and TK.
That said, an unprepared Strange dies a horrid, horrid death. With prep, I'm not sure. If there's ever been a character that's been all over the charts, it's Strange. He's got amazingingly high victories, and ridiculously low losses as well.
And since we didn't really get to see Dark Phoenix in combat, we can really only postulate what she can do. If she fights the same way that Necrom did with the Anti-Phoenix, Doc's in a world of trouble, especially since Dark Phoenix is even more insane that Necrom.
Even with prep, Doc's gonna have a hard time fighting someone that tosses small planets at him. But if there's anyone in the MU can pull of a win against DP, it's gonna be Strange.