It may be that you need to work on gear more than champ selection.
Hmm, 14 is magic affinity. What's vogoths resistance? Give him 130+ for stage 14 and he'll resist all the poisons.
make him the only spiirit affinty champ on the team, and they'll all attack him.
Ninja, UG, Apoth, vogoth, ...adelyn for more healing?