As I've told a few players, the population will spread out over time. This type of problem always occurs when something is new, and did indeed occur on retail every realm launch or new expansion. BC was probably the worst, since it thrusted entire hordes of 60s into 1 zone(The PvP was legendary though). But it's a temporary problem. Compared to the situation at launch, I've already started to notice lower level areas thinning out as the main zerg has moved on to 20s, 30s, and soon 40s. Remember that you don't have to do every quest to level, and in later zones you'll be able to kill players of the other faction. Running dungeons is also an option, as the instances are unique for your group. With so many players, dungeon groups should be common. I can also suggest everyone to try using a conformed global chat channel to post for these, such as /lfg. What we did back in retail Classic was use /lfg to post for dungeon runs, ie /lfg -> LFG DM or LFM RFD. This allows you to find groups/players across the world.
