Wow Leafshield, really interesting idea. While the Latias calcuilations have little merit, as Cobalion is not meant to switch into it anyway, the Venusaur calcs are awesome, and show that with HP investment Cobalion can become a perfect check to Venusaur, taking everything it commonly uses and crippling back with Thunder Wave. Also, Heatproof would allow speedy Cobalion to act as a perfect counter to DD Dragonite (which usually forgoes EQ in favor of Fire Punch or Extremespeed), and as an even better check to Dragon Dance Salamence and Choice Scarf Salamence (+1 LO-less EQ cannot OHKO Cobalion even after SR). Would be a really neat addition to the OU repertoire!
Thanks! I guess you are right about the Latias calls in hindsight, I guess my thought process there was moreso like "Hey look, Latias can't touch this dude!", but I do now realize that it's not as important as I had let on. But yeah, I figured people would like the Venusaur calc, as he is one of the most, if not THE most threatening sun sweepers in the meta. Knowing that you can take Hidden Power Fire comfortable even after a boost is fantastic, as you're now capable of tanking it and crippling the dino with paralysis.
I actually didn't think about D-Nite, and you are very right. Most DNite (especially on Sun teams) prefer to carry Fire Punch to hurt Ferro and Forretress, meaning that Cobalion can easily stomach the punch and attempt to TWave on Non-Lum variants and/or keep momentum with Volt Switch. Here's a calc for DD Nite's Fire Punch against the previously used 48 SpDef Jolly Cobalion:
252+ Atk Dragonite Outrage vs. 252 HP / 208+ Def Cobalion: 68-81 (17.61 - 20.98%) -- possible 7HKO
252+ Atk Dragonite Fire Punch vs. 252 HP / 208+ Def Heatproof Cobalion: 56-68 (14.5 - 17.61%) -- 9HKO at best
That does jack shit. Even at +1...
+1 252+ Atk Dragonite Outrage vs. 252 HP / 208+ Def Cobalion: 102-121 (26.42 - 31.34%) -- possible 4HKO
+1 252+ Atk Dragonite Fire Punch vs. 252 HP / 208+ Def Heatproof Cobalion: 86-102 (22.27 - 26.42%) -- possible 5HKO
Even in the sun and SR, Fire Punch is barely a 4HKO.
So yeah, I also agree that Cobalion would be a very useful counter to DD Dragons in the OU tier, and sun sweepers in general (sans Volcarona)