I would recommend going Set for Void/Phys and Nec/Pois. Go with regular suffix for Elemental resists. That will free up 5 prefix slots to use on other important things.
The individual resists aren’t good. You would still need 4-5 of each to hard cap the resists so it ends up taking up far more slots. (Hard Resist cap is 115% accounting Shred, 145% accounting Shred and Marked for Death. Not sure how common it will be to encounter both effects, and even at that, is it worth the gear spots?)
Vitality is actually a good stat now. Health regen is a primary way to mitigate DoTs. Vitality and Added Health Regen are both prefix. (Increased health regen is suffix).
You will still need Crit Strike Avoidance, a suffix, although numbers on those are pretty high and you can cap it at 100% with just 3. Flat health is also a suffix.
It really just matters what non-defense things you want, then determine what kind of affix space you have.