Any tips for 2v2 setup?

Hi - I started to dual box yesterday, and found some really great information on this site. However, most strategies seem to revolve around having a team of 5 characters. I only have two accounts, though, so I am limited to a 2 character team.

My question is what setup would work well for:

1. two manning 5 man instances.
2. leveling somewhat fast.
3. 2v2 arena.

So far I have tried out two same/same combinations. My first was hunter/hunter, up to level 9. It was of course very fast, but I already have a level 70 hunter, so if possible I would want something else. My second setup was two rogues, that I got to level 7 for testing purposes. This became very effective once I managed to position the both rogues on different sides of a mob, so I could chain backstab everything to death. I could continue with the rogues, but fear that instancing might become hard.

Please share your wisdom with me, and forgive me if I have missed some crucial information about the two character boxing.

Well, my feral druid is in blues and can solo Ramparts and Blood Furnace, shouldnt' be too hard to 2 man.
SV is partly 2 mannable with resto + feral druid.

I dual box a Prot Paladin and an Aff Warlock, with quite effective results (both lvl 70 T4/5 Geared). SSO dailies are a breeze, also ran some instances helping friends get quest rewards.