Armor diminishing returns
The way the formula works, there is no DR on armor. However, 3200 armor is pretty much good enough. The only “DR” is how that toughness could be a different stat.
Personally, after I hit 3000 armor, I just start stacking vitality over toughness.
It kicks in, for reference you can look up a damage formula and see how damage interacts with armor. As a rule of thumb, in order to halve current damage, you have to double current armor, for example base armor for level 80 Heavy Armors is 2127, in order to get 50% damage reduction you will have to add an additional 2127 toughness for a total of 4254 armor.
But the main thing you’re going to be watching for when building your character is opportunity costs rather than diminishing returns, what can you get if you sacrifice xxx amount of toughness for other armor sets?
None of my builds exceed 3k armor (partly because I’m a damage junkie), I usually go for a balance (I’m assuming this is for WvW?)
As for the bang for your buck just remember rules of thumb like shoulders, hands, feet give you more crit damage for your buck, power scales very very well, etc.
For your specific situation, there was a thread on the effectiveness of toughness vs vitality and some number crunching to go with it, I’ll try to find it again
Edit:
http://www.guildwars2guru.com/topic/60838-math-damage-reduction-toughness-and-vitality/
This is a decent thread on the math behind damage, and he has a general rule of “how to allocate your next 10 points in vitality vs toughness” so that might be helpful for you.
(edited by lmaonade.9207)
Thanks for the info