Well I gave this deck a try at BRs, slightly difference list (went with 3 Emolga and such), but anyways:
-Ultra Ball I rarely used. I was actually surprised at how quick you could get those Gabite out, most games I was flooding mass Dragon Call T2-3. But still, I am hesitant to drop it completely, as you're completely shut out of Garchomp outside of drawing into it or Dragon Call, and there are some scenarios where this can happen (like VS Garbador). At the same time, I really want to try 2 Max Potion in over it, there were more cases I could have used it possibly. But still...not having that access to Garchomp just in case bugs me.
-I ended up trying out 3 Cheren over Bianca, think I'll try Bianca now instead. Honestly I think I could have been a bit more aggressive in drawing, I found myself playing more conservatively really not wanting to use my Junipers at all since it seemed like more often than not I was holding something I really didn't want to discard, like Catcher. So I think if I go more aggro on that route, Bianca could work well.
-Accelgor/Goth decks suck, that lock is just nasty and I think it's BS how they can keep hitting DCE after DCE just from drawing alone >.>. Eel variants with Mewtwo EX and whatever else were also annoying, usually I could still 2HKO their Pokemon regardless of Eviolite, but the fact you have to 2HKO stuff (in addition to me never drawing into Catcher to pick off those dang Eels) made them a bit of an annoying matchup as well when some of those EXs can reach OHKO damage.
-Swablu REALLY needs a dragon version, I hate how you can't grab one with Dragon Call.
Overall Garchomp/Altaria is definitely fun to play, it can swarm pretty easy, especially if you can get that Gabite out by T2 and have Emolga somewhere help out. The main problem though is that if you can't hit that Gabite soon enough, the deck slows down I think to a point where it's harder to recover, as other decks move just as fast and if you start losing Altaria since you can't threaten with Garchomp, it makes it that much harder.