I just found it interesting as someone new to ORAS UU how much disparity there is between 1630 and 1760 (the other tiers don't seem to have as many big changes as this or at least none as immediately attention-grabbing... or maybe I'm just blind.)
Here are my experiences with some the pokemon you've mentioned:
I've been playing with Doublade recently and
really been liking it. I guess the memo just hasn't trickled down to lower ladder yet that this thing is awesome. My guess is that the double-whammy of being RU by usage and NFE makes people overlook it. If anything, the fact that it so easily and reliably stops a Slurpuff sweep should make it even more popular in lower ladder. Doublade takes physical attacks like a champ, and late-game threatens to sweep a worn-down team with boosted Shadow Sneaks. More often than not I've found this thing paves the way for something else to sweep, weakening the last few links on the enemy team for a scarfer to clean up. I want to try it on more teams in the future, as I've been very happy with its performance so far.
As for Nidoking/Nidoqueen, in any meta one of them is going to overshadow the other due to just how similar they are. Need speed and mixed coverage? Nidoking's your man. Want bulk to live those tougher hits or set up hazards? Nidoqueen's the woman for the job. I don't think it's surprising that Nidoking is favored by lower ladder; he's way simpler to use, and there is the cool factor. Nidoqueen's ability to set spikes and live hits that Nidoking can't is what makes it favored, but both are really good special attackers.
For Arcanine, the big problem is that his offensive sets are outclassed by Entei and his defensive sets struggle from being SR weak and the fact is that fire just isn't a very good typing for a defensive role right now. EdgeQuake coverage is everywhere and both Feraligatr and Mega Swampert are brutally dangerous physical sweepers that Arcanine can't check effectively or at all due to type disadvantage. You also need to run either Toxic or Roar, otherwise other fire types just set up on you. Arcanine's offensive set is actually quite good; I find running intimidate to bluff a defensive set is really nice, and even once it's revealed as an offensive set that coverage remains unpredictable (fire, fighting, dark, electric, priority, and possibly even reliable recovery; I really like pulling a morning sun when my opponent is trying to let him die from recoil). If Entei weren't in the tier, I'm pretty sure Arcanine would take his mantle in a heartbeat. As it stands, though, Entei's stats are just higher across the board, and access to Sacred Fire seals the deal as our premier fire type.
As for Abomasnow, there are two big things going for it: Ice Shard and hard-hitting grass-type moves. Ice Shard is
awesome in the UU meta, since almost all of our fastest threats are ice weak. It also breaks through bulky waters with ease using its grass STAB, fearing only the 30% chance of a scald burn. It can revenge all three of our S-rank pokemon, and can beat them if they switch in on a swords dance, and there are plenty of other things it beats too. Very much an anti-meta mon and cool to see it getting traction.
Galvantula is used for sticky web. That's it. That bulk is horrible, those offenses are mediocre, and that speed tier merely good. This thing would have fallen to RU ages ago if there were any competition at all for sticky web setters. Galvantula's fragility means he can usually only set up webs once or twice per game, so he basically only fits on HO teams that can keep up constant pressure and prevent hazard removal. I ran him back when I was a newbie, and looking back I feel like the little spider was trying but just couldn't keep up with the UU tier's power level. No surprise that he gets used in lower ladder, where reckless HO can sweep unprepared teams effortlessly, but really not good enough as you start working up the ladder.
Kingdra/Noivern are falling because there's a lot of competition for their roles. I've looked at them many times before, and on their own they look like fine pokemon... but Feraligatr is a better water-type dragon dancer, Swampert is a better rain sweeper, and I'll take a scarfed Salamence or Hydreigon over Noivern. We just have
a lot of good dragon-types to pick from here in UU, so some decent ones are bound to fall to RU. Scrafty and Trevenant, though, have no place in the UU meta. They're just too easily KO'd by too many things, and other pokemon can threaten to sweep an entire enemy team with the amount of setup these guys need to simply function.
Edit: huh, that ended up WAY longer than I'd anticipated.
