That was me on the Beta server. They have a more active Ubers ladder than Smogon's which is why I'm there more now.
Giratina-O is a good partner for Groudon, since it beats Forretress and can priority Shadow Sneak to kill Deoxys-A and Mewtwo that threaten Groudon. It's also a pretty ok switch in to non-Specs Kyogre. Palkia is generally an awesome partner too. Groudon + Scarfkia beats every single Rayquaza there is. It can also abuse Rain in case Kyogre shows up and can be your primary switch to sponge Specs Water Spout.