Raven's not a match for Phoenix, let alone Dark Phoenix. Phoenix has the ability to exist in just about any environment without harm, project force bolts of ridiculous power, create incalcuably strong force fields. She has telepathy, illusion-casting, she can manipulate time, space, matter, energy (as well as energy absorption), flight at light speeds.
Raven's no pushover under normal circumstances, but Phoenix would laugh at Superman and dance on his corpse (well, Dark Phoenix would, regular Phoenix may feel remorse).
It depends on how advanced ravens powers are you see Raven was born for the specific purpose of ending the world much like hellboy, they both are powerful but compared to other beings like the pheonix they pale in comparison i think that if raven unleashed her total and ultimate power she would have a good change of defeating the pheonix just like when hellboy unleashed his inner evil and became almost unstoppable. Its evenly matched to me.