I very rarely found myself in a situation where I needed to go back and grind in order to overcome a dungeon or enemy as part of the main story. (gamingtrend.com)
However, these are optional areas and are not part of the main story so you can comfortably complete the game with just one character. (dailyjoystickpodcast.com)
However, this is the only part of the main story line that is playable in its current state. (completegamereviews.com)