My take is: Expertise > Aim > Power > Endurance

You can get more xp/hr doing pve. However, you acquire the synergy or leveling, increasing valor rank, and gaining currency while pvping. I suggest pvping & mixing in your class missions periodically to help with the monotony of only having 3 battlegrounds.

I may be blind and make this sound like a silly question ... Is there a way to bring up the In-Game Scoreboard mid-game? Also, is there a combat log somewhere?

Level to 50.