This is aimed at theorycrafters. If that's not you, then feel free to move along.
This is a discussion of Barbarian mechanics. Much of this is still theory, and has not had vigorous in-game verification. This is as accurate as I can reasonably make it, but if in-game evidence suggests otherwise, go with in-game evidence.
This is also relatively abstract, and I make many simplifying assumptions mostly for my own sanity. "Real world" considerations such as AoE, mobility, and crowd control are valid issues that I will do my best to consider, but I'm only human.
Taking damage, using a fury generator or using an auto attack generates fury. However, you must actually hit something to get the fury. Leaping into nothing gets no fury. Environmental targets do count. Breaking the scenery will give you fury.
Fury does not immediately start generating. After hitting something, fury remains locked for about 5 seconds and then starts to degenerate. Again, hitting the scenery will keep the fury from degenerating.
HOW DAMAGE IS CALCULATED
To the best of my knowledge, damage is calculated as such:
(Weapon Damage + Static Modifiers) * (1 + %Str) * (Ability Modifier)
1 Strength = 1% additional damage.
For example, a sword hits for 8-12 at 1.0 attacks/second. The item will list 10 DPS. You have 50 strength. You hit something with Bash unglyphed.
Low Dmg = 8 * (1.50 Str) * (1.50 Bash) = 18
High Dmg = 8 * (1.50 Str) * (1.50 Bash) = 27
Avg = 22.5
Attack speed = 1.0 Attacks/Sec
In the future, I will always use average for simplicity.
Now let's say your sword now has +5 fire damage. +Dmg on other gear like a ring works the same way. The calculation is now
(10 base + 5 Fire)*(1.5 Str)*(1.5 Bash) = 33.75
What I don't know is how much of that damage is fire, and how much of that damage is physical. I currently assume it's 22.5 physical and 11.25 fire, matching the original proportions. This may be significant if monsters have elemental resistances and armor.
Now here's what I don't know, passive bonuses and % damage on items. In the previous example, lets glyph weapon mastery. We now deal 15% extra damage from swords.
There are 2 cases:
(10 Base + 5 Fire)*(1.5 Str)*(1.5 BasH + .15 Mastery) = 37.125
(10 Base + 5 Fire)*(1.5 Str)*(1.5 BasH)*(1.15 Mastery) = 38.8125
The first case is how Diablo 2 worked. The second case is what we hope is true. A similiar problem applies to %dmg on items. I'm not sure where the order of operation of that goes. There's probably different behavior if it's on the weapon or on something like a ring. I don't know if off-weapon % dmg exists in Diablo 3.