The level of the mob is just the example they use. Calculations are made based on skill tables not level. Your weapon skill versus the targets defense skill.
https://github.com/magey/classic-war...e#weapon-skill
Effectively, for each point of weapon skill above your targets defense skill gives you 0.04% increased crit chance and decreased dodge, block, parry and miss down to the minimum base value of 5%.
A level 52 mob has 260 defense. 312 Weapon skill would give you 2.08% additional chance to crit.
As well as changing the avoidance table, weapon skill reduces the damage reduction from glancing blows. A human with edgemasters (312 weapon skill) will do 95% damage with a glancing blow compared to a character with 300 weapon skill who will do 65% damage on glancing blows.