I think its major failing point is the complete opposite. Its not grindy enough. There are too many ways to get XP easily and outlevel the content. Its not as bad as Rift, but its looking to be close.
Classic WoW succeeded in keeping so many people because the lengthy leveling. Unless you did everything you needed to grind at times to level. Which slowed things down. In SW:TOR you level without grinding by doing non-heroic world quests, class quests, and bonus quests.
Do any warzones, space missions, or flashpoints and you quickly begin outleveling planets.