You should watch the MarlinPie vs Evil Rahassan match in this week's Break (
http://www.twitch.tv/8wayrun) for new anti-Pheonix technology with C. Viper and Ammy:
Step 1: Activate dark pheonix with C.Viper
Step 2: Immediately do team hyper during transformation animation
Step 3: X-Factor, which cancels Viper's hyper but Ammy's element hyper keeps going for 3-4 more seconds
Step 4a: If she blocks the team hyper, C. Viper can do the unblockable focus attack move before Ammy's hyper is finished and kill Dark Pheonix
Step 4b: If she doesn't block, finish the combo and kill Dark Pheonix. She can't teleport because the first hit of Ammy's hyper is fullscreen, she can't x-factor cause she's in the air, and she just transformed so she doesn't have any meter. Guarenteed kill.
If you don't have C.Viper, don't fret. You might not get an unblockable, but with another character (like in the link above, Magneto), you get a mix-up against Dark Pheonix while ice and lighting are filling the screen, obscuring what the mix-up is.