u/Omega___Neko

My Cartethyia is S6 from the first banner she had and i have two questions : does upgrading her Defier's Thorn from R1 to R5 worth it ? I also heard some peoples saying that at S6, adding Ciaccona to the team would be a DPS loss : is that true ? (i currently do not need to do some crazy quickswap to clear all endgame content with her, i also do not want to learn that).

Thanks in advance.