78 allres = 780 armor is only true if you already have about 1:10 allres:armor rating. That's unlikely for barbarians. What are the usual values for armor and allres on a well-geared level 70 barbarian? Just browsing some barbarians on Diabloprogress it seems something like 12.5k armor and 700 allres. In that case, a diamond provides you with 4 times as much toughness as a ruby.
Check your mitigation in this little calculator I wrote recently.
Just wanted to say thanks for sharing your awesome calculator! And just one easy question.. for % Damage Reduction.. would I just put 30% in there for a Barbarian? Not exactly sure what to input for that one.
so it has nothing to do with pvp i think.
Thanks!