Warrior + Priest

Hi,

I started playing with a friend some time ago. I'm a prot warrior, and he's a priest, probably disco. It's his first time playing, but he's doing very good. I have some experience with WoW. I've leveled up a few warriors, mainly in WoTLK. I know how to tank RDF and during questing. However, I'm considering changing spec. I don't remember the last time I played Fury/Arms or if I ever did. So I have a few questions about warrior spec with duo priest:
Does playing ARMS + Priest significantly increase the speed of killing mobs while leveling? Does Arms has more/better AoE?
Another issue is that I'm not sure if I want to tank RDF for next 40~ lvls (around 30 currently), and I'm most worried about end-game. My raiding experience is just a few random runs in SoD or WoTLK, so I wouldn't feel comfortable playing as a tank, and I'd rather try my hand as DPS.
Additionally, we don't have a guild, and I don't know if we'll join one, so do people look for random players for runs, like priests and arms or fury warriors
And lastly, we will probably want to try some world PvP, so prot is probably out of the question here.
I'm a bit worried that we won't join RDF at all and whether ARMS is viable.
I would also appreciate for guidance on ARMS.

Thanks in advance!