And how do you not identify this as a problem with your strategy? Did you ever have a character with elemental tortoise in the previous game? Did you experience a problem with fire because only one person in your party was immune to fire?

Its as if you actively try to create a problem for yourself and then act suprised when you succeed.

Have the characters who are immune to poison use that to their benifit, and avoid poison with the rest. Do not have a zombie and a non zombie close to eachother. WHat's the problem here?