Is there a valid siutation that round-robin service load balancer always bring request to APP1?

Dear all,

My company have a SP2010 production environment. The topology is:

2UAG
2APP (awa WFE)
2SQL

According to my understanding, the 2APP in the same Sharepoint farm will form service load balance by default. Hence all request come to APP server will be evenly distributed in round robin fashion.

However, when we check the server monthly performance report, APP1 have high CPU usage most of the time while APP2 have close to zero CPU usage. There are some reasons come to my mind:

1. The number of visit is very low, like 5 visitors per day.  Maybe the SharePoint round robin mechanism will reset the count after a period of idle time? Hence it brought all 5 requests to APP1.
2. The UAGs have wrong configurtion (which I have no access to check)
3. There are some components (maybe search?) only run in APP1. We do not have FAST only the OOB search feature.

Am I right and is there any other reason??