
There is no check for each separate item, so one can not get multiple Crushing Blows in one attack. All melee damage is explaining Crushing Blow, Deadly Strike, and Open.

There will be one random check for a Crushing Blow. Deadly Strike is a Diablo II combat mechanic that appears as a Chance on Hit mod. If you have more than one item with Crushing Blow, the probabilities will be added together. So, before doing the damage that you would normally do, there is a chance you will reduce the health of the monster by X% then normal damage apply to the resulting lower life.

In 1.10 Crushing Blow is calculated before your normal damage. Physical resistance does apply to Crushing Blow damage, but only if the resistance is positive. So that if a monster has 450% more life due to 8 players (or whatever the value is) the life removed is further reduced by the same amount (450% would equal multiplying by 4.5 so the life removed by Crushing Blow is divided by 4.5). The life removed is also scaled with number of players. with missile weapons, vs Champions, Uniques, Bosses: 1/16th with missile weapons, vs Hirelings: 1/20th This is a chance of reducing a monster's health by X% in a single blow.
