Dmg type and resistances
I think it would be nice to spell out what out there, what goes to what, and how we can stop them. I'll update this original post as FACTS are established. I'll begin with what I thought I knew.

Dmg types 
Physical
Pierce 
Fire (burn)
Cold (frost burn)
Lighting (electric burn)
Poison
Bleeding
Vitality (%reduction to health and vitality decay)
Life Leech
Elemental 

now to work on 
+% dmgs
Whenever it says +%total dmg it affect all forms of dmg. Every kind (expect %reduction to health)
Whenever it say +% dmg it refers to physical dmg ONLY
+% pierce dmg effects pierce dmg only
+% fire dmg effects "flat" fire dmg ONLY
+% cold dmg effects "flat" cold dmg ONLY
+% lighting dmg effects "flat" lighting dmg ONLY
+% burn dmg effects burn dmg
+% frostburn dmg effects burn dmg 
+% electrical burn damage effects electrical burn dmg
+% poison damage effects the damage of poison damage
+% poison duration continues the length of your poison with the same psn/sec
+% bleeding damage effects the damage of bleeding damage
+% vitality damage effects vitality damage and vitality decay
+% life leech damage effects the damage of life leech damage
+% Elemental damage effects Fire, Cold, lighting, and elemental damage AFAIK it DOES NOT effect any DOT(damage over times, burn frostburn, electrical)

Resistances
Physical dmg is reduced by "physical resistance" or "damage resistance"
Pierce dmg is reduced by "pierce resistance" 
Fire (burn) is reduced by "fire resistance" and "elemental resistance"
Cold (frost burn) is reduced by "cold resistance" and "elemental resistance"
Lighting (electric burn) is reduced by "lighting resistance" and "elemental resistance"
Poison is reduced by poison resistance
Bleeding is reduced by bleeding resistance
Vitality (%reduction to health and vitality decay) are all reduced by vitality resistance*
Life Leech is reduced by life leech resistance only

*More information on Vitality related and life leech related damages can be read in link
Note that "Damage absorption" is not type dependent. 100% damage absorption would be invincibility. "Damage absorption" is applied AFTER armor and resistances. It is NOT additive. i.e. 50%dmgAb +50%DmgAb = 75% DmgAb(dmgtaken*.5*.5= .25dmgtaken or 75% absorbed)