I found a way to do KAPPA’s bossfight taking no damage.
Do Talanah’s side quest line to get Lightning Hunter Bow
Stock up on ridge-wood, sparkers, and maybe volatile sludge
Get Radial Blast Valor Surge (in Interceptor skill tree)
Get Triple Notch skill from Hunter tree
When u enter the boss arena for the Tideripper, triple notch shock arrows (maybe advanced shock arrows) and fire on Tideripper until stunned
Run up and critical strike, u should be able to get 3 in
Use Radial Blast after Tideripper is not stunned, finish stunning with shock arrows
Critical strike, use shock arrows when done to stun again
Rinse and repeat