Yes, PIM processes being Priority 1 is normal, expected behavior. This is related to the fact that PIM is a security product that is designed to intercept and either authorize or block every action done on the system. 'seosd' is the main service daemon for PIM. Every running process relies on seosd. This is why seosd is assigned the highest priority allowed, so no process that is waiting for authorization will be blocked because the seosd process could not get a CPU cycle.
If you suspect a performance problem is being caused by the seosd process you should open a ticket with CA Support to have this looked into. CA would need to investigate why seosd may be stalling in order to address the performance issue.
If you are running PIM build 12.8.1 (1912) on AIX and are seeing problems with seosd, we recommend upgrading to the latest version as there are some known issues with this build related to seosd and performance.