- Your query is you are looking for a specific user. The load balancing is done using all sessions. As a result, having an imbalance for a specific user is possible. It is the total number of sessions on the nodes that should be approximately equal. I'm assuming that although your query is doing this, you are seeing an issue on a larger scale.
- Are you using any services that are node-specific. People often use services to partition workloads between different nodes of the cluster. In fact, I've never seen a good RAC implementation that doesn't use services. You can make sure different functional already preferentially run on specific nodes to reduce the likelihood of blocks being shipped over the interconnect.
- I'm not sure why jumbo frames would have any affect on the load balancing unless there is some other problem. Personally, I would probably try turning off jumbo frames to see if the problem still happens. It would be good to know if this is linked or not.
- I think you need to raise your concerns with Oracle Support, in case there are known issues with your patch level. Looking back on earlier posts I can see you are not on the latest patchset for your version...