A lot of people, in my opinion, chose the Horde because the Horde are the "bad guys", I mean bad as in good, I mean they don't know any better. They see orcs and all that barbaric aesthetics and undeads on top of that and think "hell yeah, I wanna be a baddie". In Wildstar the Dominion are presented as the "bad guys", and delightfully charismatic bad guys I must say. So I think some of the Hordies are going to pick Dominion simply because they think they are villains. I'm definitely going to play as an Exile.