I would hesitate to say that Chandelure is so useless under rain. Specs STAB Shadow Ball coming off base 145 SpAtk is still Specs STAB Shadow Ball coming off base 145 SpAtk. For instance, Tornadus-T is OHKOd after Rocks, period. Keldeo is risking an OHKO with a layer of spikes.
Hell, 252/252+ Ferrothorn is still OHKOd with Specs Flamethrower in the rain. Fire Blast is a very comfortable 2HKO on Jirachi in the rain. As far as other checks go, 252/252+ Tyranitar is 2HKOd by HP Fighting (does a minimum of 65%) and Heatran is 2HKOd with some prior damage/hazards.
So yeah. Specs Chandelure is still properly terrifying to face.
FaceFaceFace: "Genesect is like the Terminator. Scary when he's coming after you, absolutely lovely with ridiculous punch-lines when he's on your side."