My team consisted of Shulk (player), Dunban and Riki. Riki for healing because it was more than enough but even then, I had a lot of success with Shulk, Seven (player) and Dunban or Reyn, Dunban, and Melia (player). If you need to rely on healing then you don't quite understand the game.

My main team was primarily Shulk (player), Dunban and Riki for the entirety of the game once I got Riki. For superbosses I used Melia (player), Reyn and Dunban. Barely any healing.

Also, don't be afraid to try out characters you don't like compared to the characters you do like. Sharla is negligible. I barely used Reyn and Riki and Melia, especially Reyn until 200 in, and I absolutely love Reyn and Melia, but not so much Riki despite being an AI for the majority of my playtime. Riki has a pretty good AI.