Not my intention to underrate rotom-c, but rotom-w seems to be more prepaired all-around than c. In fact you are missing a great thing, Rotom C actually CANT check sun teams(can rotom learn rain dance?, seems like it could work). If rotom W and Gastrodon Are an issue you could just pack HP grass.
yes, you actually check ferrothorn and gastrodon, but then what about volcarona,heatran, fire pkmn and ice beam users?(i dont list venusaur or virizion, since both forms have nothing to check them if not packing hp ice)
Every pokemon has their niche. If you need a check to Ferrothorn and Gastrodon that can maintain momentum, etc. then Rotom-C is useful. If you have a team weak to Volcarona of course you won't use Rotom-C, but this weakness doesn't make Rotom-C useless. Just because a pokemon is weak to certain types doesn't make it unusable. Just look at Scizor, it has a 4x weakness to fire and can't beat Volcarona and yet it is consistently one of the top used pokemon. Just because X pokemon is weak to Y pokemon doesn't mean its unusable.










