WoW Classic Attack Table

Attack Percent Roll Range
Miss
Dodge
Parry
Glancing Blow
Block
Crit
Crushing Blow
Hit

Notes

All melee attacks are governed by the attack table. Each value in the table is absolute, a 10% chance to block means that all attacks have a 10% chance to be blocked, not just ones that hit, aren't dodged, etc.[2] The server rolls a value between 1.00 and 100.00 and will select the corrosponding attack on the table.

Each point in defense increases your chance to be missed, dodge, block, or parry an enemies attack by 0.04%. Each point also decreases the chance you are crit by 0.04%. This makes every ~8 points of defense ~1% avoidance.

A level 63 mob has a 5.60% chance to crit you so at 440 (+140) defense their chance to crit you drops to 0.00%.

High enough defense or spells such as Shield Block can "push" lower priority attack types off the table.

Reference