If the EMP attack had merely owned the Phoenix Avatar (Jean) instead of destroying and shattering into a billion billion pieces and scattering the ACTUAL Phoenix Force across the entire galaxy, I'd say no it's not an instant win. But the EMP almost killed the actual PF itself.
__________________
..even the outer hells are indifferent matters for they bow only to potent and archaic Nodens.
I'll attribute that to PIS + a defensive lapse. How else do you explain an entity that can block attacks from abstracts, heal abstracts, survive in core of the sun then consume it etc. owned by something so minor.
In a forum fight starting off face to face DP would easily transmute Xorn and spread his atoms throuout 616 no prob. If he could be decapitated by Logan, shouldn't be hard at all. Soon as the fight starts it's over under these circumstances.
This. And add to the fact that she said "in-story" she doesn't know how long they'll let her stay. Besides the point Rachel as the weaker of the avatars threw planets, and your telling me Jean whose been described as the Force's physical embodiment can really be taken out by a Planetary level Emp. PIS if I've ever seen it when the Sun produces stronger ones and she'd just can from there, hell she got back by manipulating on a molecular level the Sun's very energy.
Phoenix ate a star.... one of those glowing balls of fusion in the sky...the thing that emits radiation nonstop.... yeah an emp would definitely do something to phoenix.