How do I determine which difficulty my level 70 Diablo 3 character should play?
The easy answer would be try a few difficulties and see how hard they are and how I feel about playing character X at difficulty Y. But that is subjective. I am looking for something as objective as possible: I know this question is not strictly objective but I am sure the community has some sort of guideline.
Perhaps a chart or table that says "to get the most out of Master, your character should be in this stat range. Below this you will struggle, above this you are wasting your time."
For example, I have a 70 (32) wizard with 232k damage, 4.4m toughness and 15k healing (this question is NOT about my wizard, just using it as an example). If I walk into a Normal game I would expect people to tell me it is a waste of my time, just as I would expect players in Torment VI to say this character is not ready yet and needs more time on lower difficulties to gear up. What I have found is Expert seems to be the right place, but I cannot explain why using objective means.
Part of the reason for asking is this: if I enter a game that my character's gear says I should breeze through but I do not, perhaps the problem is between the chair and the keyboard and I need to evaluate skills and strategy.
Edit: my end goal here is eventually to be in Torment for the better loot and the prestige of being able to handle the highest difficulties. Along the way I want to gear up from drops and gambling (so Expert would help with bonus blood shards) as well as gain paragon levels (although that is more a side effect of grinding for gear than anything). I just want to have some objective idea of where I should be along the way.