off the top of my head id say use haku for the 40% stat barrier

as for being a water main ive seen heal and control archetypes depending on which one you choose i can give you more advice

heal water mains usually are easier to kill due to wasting their main on healing, the control type water mains though are quite fearsome because they dont let you do anything, what with shark bombs and debuffs from charkra blade and acupuncture