I have no reason to post this, which is reason enough.
I don't know. If you play with a team of Shulk, Sharla, and Reyn, controlling Shulk and making the most out of everyone's roles, it just seems to be an ez 123. I find that is a team that is very general and able to handle the widest range of trials; if you are more capable and confident, you can get by with just about any balanced team.
Are you using gems? Are you using a reasonable set of equipment--- that is to say, if you are having a hard time staying alive, will you adapt your gear and strategy? Are you taking advantage of skills and skill links? Upgrading your maximum art levels and investing your AP appropriately? Are you prioritizing the right targets? Locking down the right targets? Changing characters as necessary--- such as controlling Melia when Ether-based attacks would be preferable?
The combat system is relatively slow... So it's more about tactics and decision making. I don't really think you need to do all the quests, since I found when people do that they just feel overlevelled. Perhaps you are just not taking advantage of one of the systems and are not as powerful as you could be.
Also, on that end note, are you liking Mother 3?
Edit - Also, Xenoblade Chronicles does have New Game+, but I think it will just make the game easier.