True, true, but there's a few things you may not have noticed:
- Protect exists. So the set is Ingrain/Leech Seed/Protect/Flash Cannon or Flamethrower. So no Toxic to punish Ho-Oh (which completely wrecks this strategy btw thanks to Regenerator) and Primal Kyogre? Also, one of them's not running STAB which means the point I made with Substitute users still stands if Flamethrower's used.
- Both analyses of damage ignore Ingrain, so not only is the heal amount lowered in your math, but Celesteela has a free switch. The top one's higher limit will screw Ingrain, but if it doesn't KO, it guarantees at least one Flamethrower or Flash Cannon off, which, when Celesteela faints, makes a revenge kill for, say, Kyogre, much easier. Ingrain isn't included in the Showdown calculator, but even if it was, like you said, Overheat from support Pdon still obliterates you, and you're forgetting about Swords Dance Fire Punch Pdon, which sets up on Protect and no amount of passive recovery will save you.
- The set in question is a special set, meaning Intimidate does nothing. Why special over Heavy Slam?
- Ubers is 6v6, not 1v1, so anyone can simply switch to Marshadow, Kyogre-Primal, etcetera, and therefore completely ignore the fact that the matchup is bad, at least for the time being. So you're basically judging the viability of this mon because of having 5 other teammates? Might as well nom Golduck, also.
- The set in question is used in practice (mine, at least) where Celesteela faints after some chip damage and lets another Pokemon take down a few Pokemon. Any mon can chip at another mon for its teammates. Ferrothorn and Mega Venusaur are also Leech Seed users.
- A switch into Marshadow with a Sash and Spectral Thief exists and is viable. Ok?
- Ingrain isn't used first turn. This also means that Precipice Blades will do nothing until Ingrain is actually used. Overheat/Fire Blast still obliterates Celesteela.
- Most P-Don use Fire Punch instead of Precipice Blades on Celesteela. No shit.
- Do you really see everyone putting out replays on this thread when they reserve a Pokemon? I asked for replays because your set is really out there, dude.
Theory isn't everything.