I think Gastrodon deserves an analysis for a number of reasons. Gastrodon is simply an excellent check to Victini, Arcanine, Zapdos and Nidoking . A 252 HP / 124 Def / 76 SpA / 56 SpD Modest spread with Leftovers is never 2HKO'd by LO Victini's V-Create or Zen Headbutt, and always survives Final Gambit if it hasn't taken prior damage. LO Arcanine can't 3HKO with Flare Blitz or 2HKO with Close Combat, and with lowered defenses both are take out by Surf with certainty, unless Victini has HP investment for some reason. If it does, it's Trick Room Victini, and that could mean it's in a whole other world of trouble. Zapdos can't do shit to Gastrodon without HP Grass or Toxic, and even then HP Grass doesn't OHKO Gastrodon without a Life Orb. Nidoking can't take out Gastrodon with a combination of Ice Beam + Earth Power, so basically Gastrodon can switch in on any attack other than Earthpower and KO 100% of the time with Surf. LO Kingdra is also walled, it can't OHKO with Draco Meteor and Gastrodon can just heal off the damage. I don't think Quagsire could manage any of this so it's definitely not outclassed imo.
Storm Drain's buff also makes Gastrodon a great check to bulky Waters that lack Toxic, Protect can be used if necessary to scout for Toxic or HP Grass. Sand Force can also be used to give Gastrodon an effective base 130 attack stat when using Earthquake or Stone Edge with a max attack Curse set. And Sticky Hold as usual is useful at rebuking Trick users like Deoxys-D.
Of course, I'm not biased at all... lol.