AC over HP?

[Zeelot]

A good way to think of it when choosing upgrades is 1 ac = approximately 7hp worth of usefulness. Therefore, a GER is a little bit worse than a 5ac/55hp ring for tanking.

This is a ballpark figure though.

Also, you should prioritize HP/resists in fights with high damage AEs or casters and AC on fights where it's primarily melee damage you are worrying about.