Used Boiling water against a 2 rankurusu's with the same stats during rain. One with magic guard, the other has Dustproof.Dustproof: Does it also protect the Pokemon from boosts in move power from weather (for instance, a Water Spout in rain will only deal damage of Water Spout in normal weather)?
The damage difference was negligible as such dustproof does not ignore any boosts from weather conditions like Air Lock does.
I suppose gamefreak gave rankurusu both abilities just to piss off Wifi Breeders