I am in two 3vs3 arena teams, with my rogue (main) and my priest(alt).
My partners when I play as rogue are a MM Hunter and a paladin, we are currently at 1813 (arround 2k last season) and I play combat/swords.
When I'm on my priest my teammates are a MS warrior and another MM Hunter (a different one), currently at arround 17xx.
The spec of a rogue really depends on your playstyle and to a part also on your teammates. Say for example your partners are a warlock and a priest, or a mage; it is unlikely that you will be focused first. So a 41/20 will give you the most benefit, because you can almost every time beat up the enemy caster/healer what ever.
But when you play war/pal/rogue you will yourself often see as the primary target. So a combat build (preferably maces) will give you a little advantage.
Depending on your partners your role also changes. Have a warrior as partner, expose armor, stun and call burst, maybe blind the healer if possible. Have a caster as partner, try to cripple their melee dps, interupt heals/fears/sheeps and do as much damage to the focus
as possible.
I suggest as a first goal, try to get to 10k hp unbuffed, without sacrificing to many damage stats.
In the 5vs5 bracket that changes of course, but I don't play that bracket anymore (with my rogue) because I think rogues are bogus in 5vs5
