Runes of Magic US / AU

In my opinion unless you go healer your best pvp choice is Warden/Scout. It also does good in PvE although healers are always needed in siege and instances. Druid/warden for siege war and druid/scout for instances would be my choice.

Mage/warden also does good in both pve/pvp. but you'd have to ask someone who plays mages.. i just don't.

P.S: i'm no healer so i'd go Warden/Scout

What follows is my opinion:
I would not worry too much about your third class unless for some reason you cannot stand one of your current class combinations, or, there is some pressing need for a particular class type being driven by outside influences. I'm not going to try to tell you how to play your character, however, I will levy some advice. There are not enough quests in the game currently to level three or more classes all the way. If you try to level all three classes equally you will run out of available quests probably around Thunderhoof Hills, i.e. not even halfway into the game. This will leave you with the unfortunate option of doing daily quests till your eyes bleed, or you get bored and quit.

The game is designed, really, for two classes optimally. Your best bet is to stick to two classes as far as you can. Then you can think about your third class. When they introduced the third class they also introduced the fast leveling zones of Coast of Opportunity and Xaviera. These two zones and their quests were enough to take a characters third class to level 50-55 which is viable. If you use these two zones to level your primary....by the time you get to your tertiary, the old zones will reallly drag.

I say, play a little first, get to know your current two classes. If you hate one of the combos, then pick a third that you will like. But chances are, if you hurry into this you may not get the results you thought you would.