This is my guide for arena priests along the healing persuasion. I'm only 2100 atm so not of the best but not of the worst either.
1. Theres a few different specs that are great for arena healing, one of which is the disc/holy tanking priest. WorldofWarcraft.com -> Info -> Classes -> Priest -> Talent Calculator
2. The second type is the pve/pvp hybrid which focuses more on + healing and less on the survival aspect. This spec however does give you blessed resillience which will help against crit dependent teams WorldofWarcraft.com -> Info -> Classes -> Priest -> Talent Calculator
3. The last spec I have is the laughable but still decent smite mage spec. This spec works great for those running with a paladin and who have high amounts of crit. It gives you some healing capabilities and some damage output, just your mana pool doesn't last. WorldofWarcraft.com -> Info -> Classes -> Priest -> Talent Calculator
Ok now for the teams.
1. I can only speak from experience on 2v2 and 3v3 teams, but theres a few combos you can run. The first of which is the Hunter/Priest combo. This combo works best with the tank build and if the hunter is Marksman with a scorpid pet. This is a very tough team for a survival team to beat because of mana burn + improved viper sting. The scorpid is also key to stack poisons which block the cleanse of the viper sting.
2. Another great combo is the priest/MS warrior or priest/combat rogue. These teams are just a outlast the other team combo and work decently with most specs.
3. Priest/Warlock is great if your lock is affliction. all the dots with the added bonus of no ability to dispel because of UA makes it easy to drain an enemies mana away. This group works best with the tank type priest again.
4. Last but not least is the Priest/Paladin combo which is great with the smite priest spec. The pally can be either ret or holy shock spec. Once judgement of the crusader is on the target + sanctity aura is up you have one hell of a burst damage team. Also holy only has a little base resist =D.
For 3v3 teams priests should avoid them at all costs if healing. The best 3v3 team I ever saw was a disc holy priest holy paladin and MS warrior. How this team works is the pally and war run out and engage the other team, then the priest rides around the back and begins mana burning the other healer and helps heal their warrior. This team is highly based off a well geared warrior.
The last part of the post is some tips on priests actions in pvp.
1. If you see a priest running towards you, be prepared for a fear, once you hit bracket 2000+ however you have to be careful if your timing WotF and CoS because most priests will run at you just to make you burn a CD without doing anything.
2. Never put up fear ward until you see your enemy. If you see a warlock or another priest in 2v2 save it till you see them casting fear at you. A hard to time trick is when the priest runs at you because this could be a feint meant for you to cast your ward so they can dispel it, or the real deal. You just have to use your judgement.
3. For those pesky mages who like to polymorph you when your trying to heal your buddies, blizzard gave us a great anti polymorph spell Shadow word death. Time it to right before the mages polymorph casts and you can deal a little damage to him and when the recoil comes back it will break the sheep.
4. Above all else if the class is a caster use mana burn often. it will force classes to use interupts on your shadow tree to stop you thus leaving your holy tree open for when you need it most.
5. and finally hotkey mass dispel to a easily accesible key because with imp mass dispel, you have your anti pally button on the rdy.
Well hope you learned something from this wall of text. Thanx for listening, just felt like I should contribute since I haven't in a long time =P