Instead of Tenta/Starmie, have you tried using:
Melotic (Level 100)
Nature: Bold
EVs: 6 Def, 252 SpA, 252 SpD
Item: Leftovers
Ability: Marvel Scale
Moves: Rest, Sleep Talk, Scald, Recover
This rest talker serves me as a double tank. It naturally walls Sp.Sweepers, but with the combination of...