I couldn't find any recent post about this so i'll just ask you guys.
What is a good partner for a warrior? Both 2's and 3's?
As of right now Warriors are really viable with almost any class, they are a high burst and high defensive class (if played correctly). Good Warriors team in 5.1 are BM Hunter / Arms Warrior / Holy Paladin (KFC). This composition was much more powerful at the start of the expansion as it is now. I actually play this Comp on my Hunter, fair warning this comp is heavily reliant on the Warrior. If your Warriors is not experienced be prepared for a world of headache.
War / Mage / Shaman (or Druid). War / Feral Druid / Shaman. War / SPriest / Holy Paladin. War / Enhancement Shaman / Disc Priest. All of these comps are really powerful. Though, be warned I am not sure where Warriors are going to be after 5.2. It appears as if they are getting hit with the nerf bat. I'm sure they'll be okay (they're Warriors...), just don't get too comfortable with your comp - think ahead.
As for 2s, War / Holy Paladin, War / BM Hunter, War / Shadow Priests are the best 2s comps for a Warrior in my opinion.