Well, it looks mediocre, but coupled with Prowl it might be pretty good.
Currently there's an issue with Prowl/Supercharge and AoEs -- Supercharge falls off as soon as an ability hits, which can even happen in the middle of an ability. For example with Pounce, Supercharge will only apply to the initial damage; it will fall off before Pounce does its bonus damage for going first, so that portion of Pounce doesn't get the Supercharge buff. Similarly for AoEs, Supercharge only applies to the initial hit on the frontline pet, and doesn't modify the damage to the backline pets (e.g. try this with Personal World Destroyer's Supercharge+Quake).
In 5.2, they're changing Prowl/Supercharge to last 1 round instead of lasting until you hit something. Hopefully this means that it will modify all of your damage for that 1 round.
If that's the case, then Prowl+Flux could be pretty mean. With a breed 8 FFF, the initial hit will be 2.5*(12/20)*(322+20) = 513, and the backline hits will be 2.5*(9/20)*(322+20) = 385. This is 1282 total damage in 2 turns -- that's still quite a lot!*
This version is not nearly as convenient as Supercharge+Wind-Up, which is good--you can't just slot FFF into any team and have him be effective. But since it's so much damage, I expect people will find a way to use it--probably in an AoE team built around it (e.g. 2x FFF + 1x sweeper pet, such as a flyer with Alpha Strike/Predatory Strike). And although you probably won't have a speed advantage when you use Prowl+Flux, even if the frontline pet dodges, the backline pets will still take 385 each.
* the basic issue with Supercharge+Wind-Up is still an issue here: stacking multipliers. Flux is 1.5, Prowl is 2.5, so you end up with a total multiplier of 3.75 for 2 turns.