Its not additive.
I think the maths works like this:

1-((1-0.25)*(1-0.15)*(1-0.65)) = 1-(0.75*0.85*0.35) = 0.78 or 78% dmg reduction

For loh/hp regen, both are reliable.
Hp regen ticks every 0.5 sec(half of the displayed value), and loh depends on your attack speed.

But since dh has imba skill loh multiplier+crazy ticks per second, loh are more valuable.

For pvp oriented players, balanced approach is more optimal, since I dont think caltrops/grenades/turret will be as reliable in arena.
Also, I think vit(hp) plays an important role too.Its useless to have high armor/res if your hp are like 20k only.For this I think a helm with amethyst socketed in is a must for any tank/balanced dh.( which I dont have yet )

p/s:crazy regen+hp man

This post has been edited by nightshade_nova: Jul 25 2012, 10:20 PM

Ppl always says that melee takes 30% less dmg, but forget that ranged class does 30% more dmg.