Effective HP is all that matters really
60k hp low res low armor <<<< 30k hp 1000 res 10000 armor

stolen from reddit:
http://i.imgur.com/kSv3g.png
- check the grid for your armor/resist, and multiply your life with the number from grid. That's effective hp.
Also there is %dmg reduction and %dmg reduction from elites... not sure where it applies, first or last, and there is also block amount, again not sure when it applies.