I love Will-O'-Wisp. It's so cool both thematically and mechanically. :D
It's a weird admiration to possess, but it's genuine. Poisoning, Lulling and Paralyzing are common and rather dull in my eyes (although I like using accurate sleep for very different, less interesting reasons), but Freezing and Burning? Now that's exotic! And of the two, freeze has been nerfed down to neater, nippier sleep, but burns deal damage while reducing Attack - which happens to be very much in Gardevoir's best interest as a defensively weak fighter. :3
Offense + Defense in one action is still sweet to me, it's why I hold such a soft spot for the Bubbler, and also it's ghost fire that plays to Gardevoir's oft-overlooked spooky traits while rounding out an offensive build wonderfully. It's absolutely excellent stuff!
7/10, it's 85% accuracy.