I think noone can give you exact numbers, its all about what do you feel would be comfortable for you.
Also i'm guessing you said that you play melee wizzard, isn't it some speedfarming build ?. The thing with speedfarming builds is that they are for speed farm lower rifts, they aren't really for pushing, just because they lack survivability (especially ingeom builds).
About what's best, it really depends on class and build, as a wizzard you will prolly value armor more than all res, because you already have alot of all res from int. Vit you will find anyway on some pieces of gear, don't think anyone actually gearing for vit. One thing is that vit is in most cases better than %life.
Vit + %life + all res + armor those are stats that affects your EHP, basically toughness stat that you see on ur char screen is your EHP.
Life regeneration - can't really help here it heavily depends on spec you play. Some classes that hit very fast uses LPH, some can use life per resource. One thing though i wouldn't put life regeneration skills in same category as vit/armor/all res.
Sometimes more damage = more toughness, stuff that dies fast won't hurt you (its not the case for high grs but could work for everything under gr 70).
Sometimes your survivability is your gameplay, make sure that you fully understand ur build and its defensive options.