I've found that rain is a very competent weather. One of the few teams I lost to while using hail was a fantastic rain team that mcMeghan was using. the only reason I was able to come very close to winning in the first place was my SpD snover.
I've been thinking about Gorebyss counters; has anybody ever tried lombre? it would be something like Substitute/Leech Seed/Protect/Hydro Pump. Hydro Pump is unfortunately not 100% accurate, but if anything, it's largely neutral and hits somewhat hard.
Rain is pretty good down here, just about as useful as Sun imo. It's hard to have successful counters to 100% accurate Hurricanes, Thunders, and ridiculously powerful Hydro Pumps, and there are various different types that can take advantage of the downpour.
Unlike Sun, which really only has Fire, Grass, and a few things that don't like their Water weakness, Rain has Water, Electric, Flying, anything with Dry Skin or Rain Dish, Swift Swimmers including Armaldo (which is scary when it actually out-speeds you), and a bunch of things I probably forgot about. O_O
I'm really surprised I haven't seen more rain teams around, as they have the potential to be the best play style down here.