I made little spreadsheet to answer my own question: How do you know what gear is best?
I didn't go crazy with it. I just made it work for barbs and only did the affixes that I cared about. The crit damage and crit % are cut off due to screenshot:
The blue columns are %'s of how much that particular stat is maxed out. It could assist a person on what to upgrade next.
The bottom part is the calculations:
I think most of these calculations are correct, or are really close. I think the damage one is the least accurate, but it's within 50-100 damage of what it says on screen after trying various things with it.
Basically, I can put in values at the top, and it tells me where I am increasing or decreasing compared to my last gear set. The only bad thing about this spreadsheet is that you have to copy over the values to the next column before you start modifying the gearset - it's not smart enough to remember your old values.
I guess the only thing I don't know how to make the spreadsheet answer is, "Is 10% loss in DPS worth 10% gain in effective health?" That's a good question!