In terms of classes, trying to cover all three roles between the two of you is a good target. When you guys are questing together by yourselves, having one person be DPS and the other healing helps keeps downtime to a minimum. And if you guys decide to use the Dungeon Finder, having one person able to heal and the other be able to tank ensures you'll never have to wait long in the queue.
Blizzard has homogenized the classes over the years so there is a tremendous amount of overlap between the classes and specs. As long as you guys cover the three class roles, feel free to choose whatever fancies you.
For reference the hybrid classes are:
- All three roles: Paladins, Druids
- DPS + Healing: Priests, Shamen
- DPS + Tanking: Warriors, Death Knights
If you're going to take my advice about role coverage, you'll want to avoid Mages, Hunters, Warlocks, and Rogues as they can only be one role: DPS.
Since you're talking 1-85 play, Death Knights are off the table as they start at level 55.
Putting it all together:
- Person 1: Paladin, Druid, or Warrior (to cover tanking)
- Person 2: Paladin, Druid, Priest, or Shaman (to cover healing)
In terms of professions, I'd avoid the heavy crafting professions that take a lot of time to level up and are usually taken for the Bind-on-pickup endgame recipes: Blacksmithing, Tailoring, Engineering, Leatherworking. Instead, focus on the professions that'll let you help each other out while leveling, like Enchanting and Alchemy, or the gathering professions, like Mining and Skinning, which will prove lucrative and won't require too much (if any) time soloing.
You might be fine tanking normal 5-mans in your DPS gear (not Heroics) but if you want to get anywhere, you will need to pick up some more gear. Look for high stamina plate pieces with Dodge, Parry, or bonus armor, and shy away from crit.
Yes, you should absolutely change your gear when going from a DPS spec to a Tank spec (or vice versa, some feral druids excluded).
Best Answer
For PvP, Subtlety is the current king of specs. For Shadowstep, Shadow Dance, Preparation, Premeditation (Gets combo points to get Recuperate rolling after a Vanish), massive Ambush damage, and faster Stealth movement. All three are decent for PvE leveling, with combat being the best for multiple enemy encounters. There really isn't a "wrong" spec for leveling. If you are on a PvP server and want to have the best PvP abilities all the time, I would level Subtlety spec.