Oh, I just noticed your post saying that phoenixes won't turn into ashes.
In that case, if absolutely everything gets blown up, there's no possibility that this card every gives you any kind of advantage right? I actually agree with you now, after thinking about it, and I see it it as UP now, ironically.
Since it uses up all your fire quanta, and no any of your opponent's quanta, and the same effect is applied to both sides of the field, it's really hard to put this in any kind of feasible deck. It just never gives you any kind of proper advantage to be worth the card slot or quanta.
In that case, whether it's seen as extreme OP or extreme UP, there's really no need for this card to be in the game, I have to say.