Although Sand Teams are certainly the most dominant weather according to usage stats, I feel that in the up and coming weeks Rain will definitely prove itself to be a force to be reckoned with in the Dream World Tier. Having been an avid user of Sandstorm for months, I have delved into trying Rain Teams, both Offensive and Stall based. I can definitely say that offensive Rain Teams are a really big threat in the current metagame. Pokemon such as Keldeo and Manaphy always cause problems for the more common Sandstorm teams, as generally most Sandstorm teams lack a solid
answer to Keldeo or Manaphy.
Choice Specs Keldeo in itself is something that all teams should fear, regardless of their weather orientations. Just looking at the 1337 usage stats, very few Pokemon can safely switch in on Keldeo, and actually do something back. Tyranitar, Chandelure, Excadrill, Skarmory, Deoxys-S, Landorus, Terrakion, Gliscor and Mamoswine are all OHKO'd by Keldeo. A very good option for any Rain Offense Team.
The most effective Genesect set that I have used is the Standard Choice Scarf set, I have tried Rock Polish and even Expert Belt versions of Genesect but Scarf has definately been the set that has consistently won me matches. Sash Genesect is still a very viable option, given the very fast paced tempo of Dream World. Although Sash Genesect does very well in bluffing the Scarf and maybe getting an extra kill on the opponent expecting you to be locked in to a move, the Scarf version for me will always be better. I find it a lot easier straight up forcing switches with Genesect as some opponents fear a potential Ice Beam / Flamethrower / Thunderbolt.
So, would you say its even more popular than sand? Because I thought Tyranitar was used on like, 70% of the teams here or something...
Sand Teams may be more popular than Rain Teams, but I definitely think that Rain Teams are coming on the rise in the near future. It seems to me like Rain Teams are slowly beginning to get the upper hand on Sand Teams. The dominant forces of Offensive Rain Teams are troubling to many variations of common Sand Teams. For example, Choice Scarf Politoed causes a lot of trouble for Offensive Sand Teams. The bread and butter Sand Teams generally only have maybe one Water resist, or two at best in the form of Keldeo / Breloom. Neither of which will continually want to be subjected to Rain-boosted Hydro Pumps. What happens when your Water resist is down? Your Garchomp / Gliscor are outsped and revenged with Ice Beam. Excadrill is no longer a threat when Sand is down and Rain is up. Even your specially defensive Tyranitar (252HP/176SDef) takes 42%-50% when Sand is up, and has a chance of OHKO'ing when Rain is up. Sand Teams will definitely have to be a lot more wary of Rain Teams on the rise.