Game Mechanics

:arrow: Crushing Blow

CB: damage 
-Default: 1/4th 
-vs. Players: 1/10th 
-vs. Hirelings: 1/10th 
-vs. Champions, Uniques, Bosses: 1/8th 
-with missile weapons, default: 1/8th 
-with missile weapons, vs. Players: 1/20th 
-with missile weapons, vs Hirelings: 1/20th 
-with missile weapons, vs Champions, Uniques, Bosses: 1/16th 
This is based on base hp not the multiplier from people in game. base is 300% in HU so the HU table looks like this.

-Default: 1/12th
-vs. Players: 1/10th
-vs. Hirelings: 1/10th
-vs. Champions, Uniques, Bosses: 1/24th
-with missile weapons, default: 1/24th 
-with missile weapons, vs. Players: 1/20th 
-with missile weapons, vs Hirelings: 1/20th 
-with missile weapons, vs Champions, Uniques, Bosses: 1/48th
This is with 1 to 3 players in game with more players in game the boss life will go up more so the % will go down even further.

Crushing blow is based on enemys remaining life. If so, at 50% remaining life on a boss, a melee crushing blow will remove 1/48th of the bosses maximum life. (With 1-3 players in game)
Amp damage works with crushing blow by lowering bosses physical resistance. Since all HU Bosses have physical resistance, If you land a crushing blow on an enemy with 50% physical resistance you will only remove 1/32 per hit If however you amp that target and take him to 0 reistance or lower you will remove the full 1/16. If a bosses resistance goes below 0 the crushing blow will not get stronger it will always remove 1/16 no matter how much lower that 0 the phys resistances are.

:arrow: Deadly Strike/Critical Strike

# Deadly Strike (DS)/Critical Strike (CS) are both a chance to double your Physical damage.
# They apply to both Melee and Ranged attacks, but not to Spells.
# They do not apply to Impale, Dragon Talon, Dragon Tail, Dragon Flight, Sacrifice, or Smite.
# They do work with the Blade Traps.
# Skills that convert Physical damage to a different type (Magic, Fire and Cold Arrows, Lightning Bolt, Fists of Fire, Berserk, Concentrate, and Frenzy (when synergized by Berserk)) do so after DS or CS are applied, so converted damage is doubled.
# They will modify your final Physical damage with Vengeance but have *no* effect on the Elemental damage caused by Vengeance.
# Sources of Deadly Strike stack except from a weapon which is not being used to inflict that particular blow.
# Different types of Critical Strike do *not* stack (e.g. Barbarian Weapon Masteries and Amazon Critical Strike).
# There is no point to having more than a 100% chance of DS/CS.
# Critical Strike and Deadly Strike have the same mechanics and only one of them can trigger on any given attack (so a player can't get quadruple damage)

:arrow: Open Wounds

This is a chance of making a monster bleed uncontrollably. They lose health while bleeding. Open Wounds Items stack in most cases.

Duration: 200 frames (that is 8 seconds).

The damage per frame seems to be the following (where Clvl is the attackers level, that is the player's level usually):

Clvl=1-15: (9*Clvl+31)/256
Clvl=16-30: (18*Clvl-104)/256
Clvl=31-45: (27*Clvl-374)/256
Clvl=46-60: (36*Clvl-779)/256
Clvl=61-99: (45*Clvl-1319)/256 

If you prefer per second, just multiply by 25:

Clvl=1-15: 25*(9*Clvl+31)/256
Clvl=16-30: 25*(18*Clvl-104)/256
Clvl=31-45: 25*(27*Clvl-374)/256
Clvl=46-60: 25*(36*Clvl-779)/256
Clvl=61-99: 25*(45*Clvl-1319)/256 

Some examples:

Clvl 10: 11.8 per sec over 8 seconds for a total of 94.5 damage. Clvl 30: 42.6 per sec over 8 seconds for a total of 340.6 damage. Clvl 50: 99.7 per sec over 8 seconds for a total of 797.7 damage. Clvl 70: 178.8 per sec over 8 seconds for a total of 1430.5 damage. Clvl 90: 266.7 per sec over 8 seconds for a total of 2133.6 damage.
(Possibly changed numbers for this mod)
Also, the damage is divided by 4 for a player target. In addition, for a missile versus a player target one should divide the damage by 8 instead.

Finally, versus bosses and champions (could be just bosses or special bosses) the damage is divided by 2.

It is possible to get up to 100% chance for Open Wounds. Anything above 100% is discarded. 

:arrow: Ignores Target Defense (Armor Class)

This ability will not work on Unique Monsters, Super Unique Monsters, Hirelings, other players, and Act-end bosses.

What the game does is that set the Defensive Rating of the target to 0. That means it simplifies to:

AR = 100 * 2 * alvl / (alvl + dlvl)

AR = Attack Rating; alvl = Level of Attacker; dlvl = Level of Defender.

The Class Bonus to level of attacker is:

20 for Barbarians and Paladins
15 for Assassins
5 for Amazons and Druids
-10 for Necromancers
-15 for Sorceresses

So there is still an effect of the level difference on the chance to hit and there is still a minimum of 5% and a maximum of 95% chance to hit.

:arrow: Absorption% (Or Absorbs)

Absorb% heals the player - which is equivalent to resistance. If you have 5% Absorb Fire, 5% of the Fire that would hurt heals you instead - roughly equivalent to 10% Resistance. It has a cap of 40%
Straight "Absorbs xx" is not active here so there is no way to heal from elemental damage.

Slow is treated as the opposite of FCR, FRW, Faster attack speed. Caps include 50% per source vs players/act bosses, and 90% for normal monsters. (sources are slow target, chill, holy freeze ect). In addition there are minimums like attack speed can't be lower then 15% of base animation speed.

Credits: Purerage