https://www.purediablo.com/forums/threads/best-darn-act-2-merc-ias-table-period.853/To quote the site
"How often will my mercenary use his Jab skill instead of a normal attack?
The short answer is: The chance of choosing Jab over normal attack increases slowly as your mercenary gains levels, going from about 80% at clvl 50 to about 85% at clvl 98. Therefore Jab breakpoints should be prioritized over normal attack breakpoints."