To clarify, because you mention getting torn to shreds from missing 20% resistance: Resistances in Last Epoch do not work like many other games. The reason for this is that enemies have passive resistance penetration based on area level, up to 75%. Because enemies will at level 75+ fully penetrate your resistances, it means the game is actually balanced around having 0 effective resistance. The result of this is that missing resistance is much less harmful. Being at 50% resistance in Last Epoch instead of 75% means you’re taking 25% more damage as enemies penetrate 75% resistances bringing the result to to -25%.
In other games, being at 50% resistance instead of the cap (75%) would mean taking 100% more damage than the 75% resistance damage is balanced against. the higher the resistance cap is, the more each point of missing resistance matters. In Last Epoch, each point has the same weight as the next, and last point.