Voice over are nice, but very very few games have them done well. you get alot of repeated phrases and half the npcs in the world sound the same. (would not be cost effective to do it other wise)

I would rather SE spend the money on solid playable content, instead of paying voice actors and taking the time to do it right where the VO is meaningful and not just muted by the players in the end. A solid game full of well designed content > a game full of Voice Acting. SWToR proved this.