Now, other games often get around this by giving each character and NPC its own space, mutually exclusive from the space around it. In other words, you can bump into things, but not stand in them, enveloping them. While such a method may be more true to life, I think WoW's way of doing things is quite handy, considering the sheer numbers of players in big cities or on heavily populated realms.
Unfortunately, it can indeed become a bit of a nuisance. I become especially frustrated in the banks, when some characters feel the need to stand in the banker, rather than in the crowd, or when I find it difficult to click target a quest-giver.
Of course, Rihlsul is right; there is an increased presence at the battlemasters. Given the fact that arena season one gear can now be purchased with BG honor, many people are on a farming push. People are also still exploring the new Alterac Valley, as it has changed so much since patch 2.3. In addition, because of the new daily battleground quests, even players who previously PvP'd seldom or even never are stepping up to bat. In fact, I often find the small excuse of doing one a day is often enough to prompt me to queue a few more.
Battlemasters aren't the only NPCs seeing more action lately either. This week, after the realms came back up from extended maintenance, ushering in arena season three and the ability to acquire season one gear with BG honor, the above shall we say "crowded" screenshot was posted in Around Azeroth.
Are you annoyed by players parking on the NPCs that you need, or are you one of the players who has a habit of doing it themselves? If you could switch to a system in which characters had their own, impermeable "spaces", would you; or are you more concerned with the newfound PvP'ers in the battlegrounds than outside their gates?