Sharla is completely disposable. Shulk is needed for some fights, but definetely not all. Tanks: Riki (with the right gems), Dunban and Seven are as good as Reyn. Some of my favorite lineups: Shulk, Dunban, Seven - My favorite endgame setup Riki (aggro and ether gems = damage dealing AoE tank), Seven, Dunban Melia (player-controlled), Riki (great healer with You Can Do It), Dunban(tank)