Sorry but Dark Phoenix wins rather easily. As the embodiment ofthe Phoenix Force she has almost no equal. The only time she has been vulnerable is when Jean has struggled to keep the power at bay. You are wrong on this point. As dark Phoenix she was again as stated only vulnerable when Jean is struggling for control. no where does it say that is happening so consider her to be at full power which means a stomp for the entity
It's remarkable how people can be quite knowledgeable about the comics, and yet so ignorant.
I'll try to explain it so it's easy to understand.
The Dark Phoenix's physical body, was created by the Phoenix Force as an identical copy of Jean Grey's body.
The Dark Phoenix's mind contained Jean Grey's memories, copied from Jean Grey's mind.
Jean Grey is not the Dark Phoenix, she never has been.
From the point where Jean Grey saved the X-men, and nearly died in the process, the person that the X-men thought was Jean Grey, was in fact, the Phoenix Force in a physical body.
The Phoenix Force, in its (relatively)newly created body, eventually went mad and became the Dark Phoenix. There has never been any "struggle for control" from Jean Grey, because at the time the Dark Phoenix was active, Jean Grey was comatose in a cocoon under-water. The personality that was struggling for control is an aspect
of the Phoenix Force.
1. The physical body of the Dark Phoenix is purely human/mortal.
2. Dark Phoenix, limited by her physical body, does not have FTL reflexes, nor is she capable of moving FTL.
3. Dark Phoenix, due to the limitations of her physical body, does not have access to the full power of the Phoenix Force(though even a fraction of that power is still ridiculously powerful).
I completely agree with you, that if Dark Phoenix actually uses her powers to attack the team, then the team is almost instantly annihilated.
However, Dark Phoenix, just like 99% of all Reality Warpers, has the weakness of purely human reflexes, durability, and speed.
Thus, the team(of which 4 of them are FTL) are more than capable, of hitting the Dark Phoenix, before
her powers actually come into play. Aka. Dark Phoenix go *splat* and the Phoenix Force is released from its physical body, and the Dark Phoenix has ceased to exist.