Moving rules with high hit counts further up in the rulebase was a longstanding recommendation to help reduce the CPU overhead of rule base lookups in R77.30 gateway and earlier. However due to the new Column-based matching feature which is enabled by default in R80.10+ gateway, moving frequently-hit rules towards the top of the policy provides only minimal gains and is probably not worth your time to pursue.
For known users the gateway already has a user to IP mapping in its cache (along with group memberships) by the time a user's traffic reaches the gateway, so I don't see why moving a rule utilizing an IA access role downwards would be a recommendation here unless you are also using something like Domain objects in the same rule or perhaps invoking the Captive Portal.
Attend my Gateway Performance Optimization R81.20 course
CET (Europe) Timezone Course Scheduled for July 1-2