Ask WoW Insider: Is there a class/spec truly viable for both PvP and PvE?

I'm on my second re-roll and finally have my character to 70, fairly well geared and have found myself in the exact same position as before... My PvE 5-man spec is entirely unsuitable for raids, or PVP, my raid spec is unsuitable for soloing or PvP, and my PvP spec is useless outside of BGs and Arenas! I was previously a Warrior, who needs to be Prot for tanking but Arms/Fury for Arena and I at least only had to bounce between two specs. Now I'm a Mage, and I have to consider bouncing between THREE specs to be what everyone expects me to be if I expect to be competitve!

I know the common answer is "suck it up and pay to respec whenever you want to do whatever you want to do" because dailies give out so much free money, but this doesn't work for my mage with however many hundreds of gold and hours of work put into getting my Frozen Shadoweave set. The problem is, I rolled a mage for the exclusive purpose of not HAVING to fill two roles with one character and not having to respec every time I wanted to branch out and experience multiple aspects of the game.

So, my question is this: Is there any class+spec out there, that is equally effective and in demand for 5-man instances, raids, solo play and PvP?