Thanks for the check, I've implemented your changes. I also removed all mentions of Toxicroak since it was QC rejected, and fixed a british spelling of the word 'favour' that managed to slip through gp.
This is now done, a big thanks to everyone who helped!
I'm still not sold on Ferrothorn, I don't feel like bulky waters are a big enough problem for rain to warrant using it. Helping to beat Azumarill is nice since Azu's a huge pain for rain but one of Seismitoad's niches is that it does well against Azumarill. Ferrothorn also helps against non-Focus Blast Thundurus, which covers up Seismitoad's other niche. Basically I feel like, if Ferrothorn is usable on rain, any team that uses it would prefer to use other swift swimmers and not Seismitoad, since Seismitoad's advantages over other rain sweepers are of less value to a team with Ferrothorn.
Water Absorb has a small niche ('Gastrodon with SR > Recover') and afaik that's what OO is for, niche stuff that doesn't deserve a main set but is worth a brief mention. I've seen a few people use it higher up on the ladder (1800-ish) so it's vaguely notable and I don't think I'm overselling it, I mention that it's almost always outclassed by other ground-types.
This is now done, a big thanks to everyone who helped!
This is based around an old reply, but the reason Ferrothorn was recommended was because, while it does waste rain turns while it is in, it actually works very well on rain teams due to it successfully beating/walling opposing Water-types reliably and, while Ludicolo works better on HO teams, it works well on more balanced offensive and bulky offensive teams - the kind that you will typically see Seismitoad on - and is definitely worth considering over Ludicolo on such teams, and it completely outshines Ludicolo on more defensive teams (unless it is the rare AV Ludicolo)
Edit: Also remove Water Absorb from OO as, like you said before, it is aggressively mediocre and Seismitoad has no niche with it.
I'm still not sold on Ferrothorn, I don't feel like bulky waters are a big enough problem for rain to warrant using it. Helping to beat Azumarill is nice since Azu's a huge pain for rain but one of Seismitoad's niches is that it does well against Azumarill. Ferrothorn also helps against non-Focus Blast Thundurus, which covers up Seismitoad's other niche. Basically I feel like, if Ferrothorn is usable on rain, any team that uses it would prefer to use other swift swimmers and not Seismitoad, since Seismitoad's advantages over other rain sweepers are of less value to a team with Ferrothorn.
Water Absorb has a small niche ('Gastrodon with SR > Recover') and afaik that's what OO is for, niche stuff that doesn't deserve a main set but is worth a brief mention. I've seen a few people use it higher up on the ladder (1800-ish) so it's vaguely notable and I don't think I'm overselling it, I mention that it's almost always outclassed by other ground-types.