PvE logic

Older toons have pretty much a basic ai that targets the weakest health and protection enemy about 90% of the time. Some newer toons have some units defined as priority target, like attacking Fives in a 501st team.

You can see old vs new ai pretty clearly on an enemy geo squad. Take night sisters in with a weaker zombie and the whole team will continually attack zombie, except for geo brood alpha, who is newer. He very often attacks others. Also Sun fac has a priority to attack someone with a debuff with his special.

Different toons have different ai, but the most common decision is they will attack the toon that they are most likely to be able to kill ie the lowest health and protection total at the time.

Some toons seem to have a target on them for all ai, chewpio might be one of them.