Hmm, I imagine it depends on what else is in the meta. Granbull hits for 160, which isn't bad, but isn't a OHKO for Reshizard (or PikaZek), and opposing fast decks that can KO every single turn has to be just as good - which is hard. It's not as consistent as Zapdos, either, so even though it should theoretically have an advantage (taking 2 hits in general to KO) it's quite easy to escape rope/guzma out of Granbull into something OHKOable for Zapdos most of the time.
I'm not even sure it would win the Baby Blacephalon matchup more than 50/50 to be honest; while it would take 3 fire discards to OHKO, and would OHKO Blacephalon, it seems to me like Blacephalon might be able to do that more often than Granbull (and any turn there's not a Granbull out there it's taking easier KOs).
My feeling is the current meta wouldn't benefit Granbull sufficiently to justify playing it, and it would have the same hard time it did in the prior meta that basically killed off the deck.
If you want to play Fairy, I'd look at Gardy/Sylveon; that looks at least interesting!