Thundurus-I seems to be too good for OU to handle. It also gives rain a major boost when it comes to winning the weather war;mainly against the likes of sandstorm. Being faster than most of OU with the ability to paralyze anything faster than it with a T-Wave already makes it a giant threat and it can stop just about any wall with Taunt. Assuming it's on a rain team a set such as Thunder / HP Ice / Superpower / T-Wave or Taunt with a Life Orb can stop a decent portion of OU. Its only downside is its weakness to Stealth Rocks and certain priorities such as Ice Shard;both of which can be handled correctly when on decent team.