I think in trying to replicate the WoW model, they maybe mistook "people enjoying levelling alts" with "very long grind". What people liked about WoW I think was that you could go to any (level appropriate) quest hub and start a quest chain. In SWTOR, you basically have to start at the very beginning of the planet to get quests.
What would have been brilliant is to have 1-5 planets exclusively for story quests for all eight classes. That way when levelling, there's Republic and Empire interaction (for those PvP junkies), and you may not necessarily see every planet. Then you just have cursory other planets offering lots of orange gear for appearance junkies, with lots of other quests.