I think Snorlax is still better than Zapdos. The boom variants, of which there are a ton, are so reliable at getting something and a half done, and the bulky Curse variants are still solid, almost forgotten in fact when all it takes is a bit of support and it steamrolls shit. This is coming from someone who's been championing Zap as the next coming of Slayer for almost a year now btw, don't think I don't know, fully appreciate and fucking love how much damn damage he dishes out! If it were up to me Lax and Zap would both be S, with big bird being the "worst" of the bunch.
Flygon is amazing and people sleep on him like crazy. I find he's more consistent on a game-to-game basis than Starmie but everyone jerks off to the offensive set now (and not that it's bad, it's very strong, but it certainly is overrated) so I might be alone on this, bad winrate (which truly baffles me) and all.
I tried Omastar and while he is exceedingly powerful, I very rarely found that I needed the extra damage he was dishing out. What I did appreciate more than anything was soaking up Aero's Double-Edges, which my hastily-put-together rain team (that once somehow managed to bust through fucking Vaporeon stall) greatly appreciated, since an EQ not only wouldn't kill but also was a Ludicolo switch. Oma is a nice pkmn,
I agree with Mag as certainly the best of the B dudes, wouldn't mind him in A. My only gripe is how the Endure set needs to be Timid and thus can't even OHKO 48 SDef Dug but overall I like him a lot. I'm not sure about dropping Milotic too far, it is surprisingly annoying to a lot of the offenses being used right now, with proper support it could definitely make up for that lack of a rock resist without much trouble; I think the double status variant is the way to go, surprise sleep really pisses off all the offensive Zaps and Boomlaxes that try to switch into it. Dunking on all the MixMence (and Kingdra!) being used is also fantastic. In any case I think it's better than Claydol, who is okay and all but Christ he has more issues than Dave Mustaine-era Metallica.
Regice is great but I find he gets worn down too easily for my liking and he doesn't quite hit hard enough, both on offensive and defensive sets. Even the max SAtk sets, which are the ones I use the most, get easily Leech stalled by Celebi, which annoys the hell out of me, and Milotic could give a shit about TBolt. I like those sets on paper for the non-Bliss teams that don't run Ice resists (like Superman) since Immunity is the better ability on Snorlax 95% of the time but even against neutral targets Regi just does not hit hard enough with its STAB, which isn't good when it's not switching into too much. The occasional TWave is pretty annoying to Ttar though, I'll give it that, but still, I've most been impressed by its damage output when HP Firing Metagross switchins... the offensive sets get chipped really easily and get trolled by Swampert of all things, I've been running Speed on mine lately just because I got so tired of it. The defensive Ices, aka the ones that heal however terribly, hit a lot less hard than 236 or whatever SAtk with 2 95 BP moves (one if you use SToss, which I think I prefer tbh), one of which is STAB, would appear to. Psych Up sets are begging to get smashed by everything that's supposed to be countered by it. A 252+ SAtk ResTalk set might be more my speed, but eh... I find Gyarados to be better because a lot of teams just get shredded by him with little effort, plus Intimidate is incredible and he gives you a safety net against Heracross. For now, I'd keep Ice below him.
Lunatone is cool, I like Explosion on him for surprise Blissey killing. I don't like running him without Mag or heavy Skarm lures though since otherwise he trolls you to hell and back... which brings me to my next point, no way in hell should Skarm be below Metagross. I know that Meta is among the best of the best when it comes to punching holes, especially since he has a ton of defensive utility etc etc but jfc being weak to Skarm is possibly the 2nd worst thing to be weak to in ADV (besides Tar/Aero) and it still manages to not just hold its own but absolutely dominate. Even specially offensive teams dislike the Toxics it throws around when backed up by Protect and being Whirlwinded around into Spikes and ugh you can tell I don't like playing Skarm.
While I absolutely acknowledge that Dugtrio is great, I still think Swampert should be just ahead of him. The last sentence I wrote for Skarm applies to Pert, even with teams being built around fucking him up he still performs consistently as hell. Plus he can always go on the offensive!
Raikou is strong. I think it should be bottom of A (if it already is then pardon me) since yeah not super consistent and all but a lot of teams just get gged by it late game, I like to use a really bulky spread to have its Subs survive Zapdos and Gengar assaults.
edit ugh fucking Maestro. I'll respond to that beautiful wall of text after some others have so I don't hog all the fun