Well, the whole world is Horde vs Aliance, that is the story, pick a side (or both like me) and go from there. I do agree however, the totaly lack of comunication between side other then raids is pretty short sighted. I had some items I wanted to send my UNdead warrior, but I was not allowed. Perhaps there will be a server where there is no HvsA at all, and it's one big happy family, or total chaos. They do need some basis for PvP I suppose, use your aliance char to go beat up on some horde, or vise versa. I for one have never in the slightest been interested in PvP in any MMO besides Planetside, cuz that was the whole point, not just a side perk. the mass of players are just not interested in RP'ing at all, so it should be no surprise that the games aren't really designed around it. L2 was a perfect example, there is a back story to each race, and who they were at war with, but 99% of the time it was all one big happy family eith the odd person acctuly paying attention to the story and playing it out.
Thats where the WoW Horde vs Aliance 'forces' players to pick a side, but if you are like me and could give a hoot less about the war and just wanna kill mobs and quest, the war means little. I have been in several areas on the outskirts of Aliance territory and helped an Undead guy beat up on stuff past his level, we didn't fight at all. I've been asked to go on raid to work some Horde players many times, but every time I ask why? There really isn't (for now) great benefit other then saying, 'yah we raided such and such!' but they all spawned 5 mins later, like nothing happened. There just isn't any point in my eyes. Now if there was mad XP gains, or the chance of some crazy ass items, then ok I might go on one or two.
I guess what I'm tryin to say is, the vast majority of players don't give two hoots about the acctual roles they play, they just for the most part think they will work best for them. Thats why most are the tank classes, paladins/warriors etc, and the spell casters/rouge are less, and the holy, well I've seen maybe 25 preists in total including me, in 2 months of beta.