I rarely run any Legendary Pokemon on my online teams since I find battles more challenging using common Pokemon than those you can only get one of normally (outside of things like the UBs where you sometimes can get more than one of). I have nothing serious against players who use anything that can be regarded as Legendary Pokemon in online battles but I hold a bit of a ruling on when and why I should use them if at all. Right now I'm trying to find Pre-Poke Bank common Pokemon in Alola that can deal with Toxapex as I already have Pokemon on my ORAS and X/Y files that can KO it with less trouble.
Mega-Lucario and Mega-Blaziken are banned for a reason, and no matter how you try to spin it, those two pokemon are strictly superior to Regigigas and Articuno. Hell, non-Mega Speed-Boost Blaziken + Swords dance + Baton Pass is banned on
two counts (Uber clause AND Baton Pass clause).
Legendaries are cool and evoke a "feeling" of power. But on Smogon, the general feel is to focus on the competitive aspect of Pokemon. As the label of "legendary" includes Pokemon that are weaker than "standard" Pokemon (like standard Blaziken), it is a pointless distinction in the Smogon competitive spirit. I'm not necessarily saying its completely pointless (in-game and Pokemon-lore wise, there is definitely a difference). But those are not the aspects that Smogon generally focuses on.
Right now I'm trying to find Pre-Poke Bank common Pokemon in Alola that can deal with Toxapex as I already have Pokemon on my ORAS and X/Y files that can KO it with less trouble.
Lots of things, even if we do this "your way" and use non-legendaries.
252 Atk Choice Band Garchomp Earthquake vs. 252 HP / 252+ Def Toxapex: 264-312 (86.8 - 102.6%) -- 12.5% chance to OHKO
252 SpA Life Orb Starmie Psychic vs. 252 HP / 252+ SpD Toxapex: 179-213 (58.8 - 70%) -- guaranteed 2HKO
252 SpA Magnezone Thunderbolt vs. 252 HP / 252+ SpD Toxapex: 168-198 (55.2 - 65.1%) -- guaranteed 2HKO
0 SpA Toxapex Scald vs. 252 HP / 0 SpD Multiscale Dragonite: 13-15 (3.3 - 3.8%) -- possibly the worst move ever
+1 252+ SpA Adaptability Porygon-Z Thunderbolt vs. 252 HP / 252+ SpD Toxapex: 376-444 (117.1 - 138.3%) -- guaranteed OHKO
252+ Atk Life Orb Mamoswine Earthquake vs. 252 HP / 252 Def Toxapex: 276-328 (85.9 - 102.1%) -- 12.5% chance to OHKO
Well that's that then, isn't it?
Plenty of Pokemon deal with Toxapex. And "Legendaries" like Regigigas or Articuno won't help you.
Talonflame is a nice Pokemon despite Gale Wings
No it is not. Talonflame might actually be worse than Swellow in this generation.
252 Atk Guts Swellow Facade (140 BP) vs. 252 HP / 252+ Def Toxapex: 136-162 (44.7 - 53.2%) -- 31.3% chance to 2HKO
No recoil damage, 125 speed tier (just 1 slower than Talonflame), only 2x weak to Stealth Rocks, far more power with trivial amounts of setup (just a turn to activate the Flame Orb). Flame-orb blocks Paralysis. Doesn't need a Swords Dance to 2HKO Toxapex. Etc. etc.
Swellow is your "Toxic-immune / Status-immune" bird of choice of NU tier. And Talonflame is going to be competing rather strongly against it.