Yeah, I spent like 80% of the game with Shulk, Reyn and Sharla. No problems whatsoever. Then I got near the end of the game and those floating balls of ether kicked my ass. Then I got to the first disciple boss battle and surprise surprise, it was surrounded by more balls of ether. I died many times. Until I put Melia on the team. Easy win after that xD
But yeah, the original team is great for most of the adventure. Very balanced and they have great lines of dialogue between them.