So in the absence of any actual way to command thralls or set their aggression level, there are currently only two ways to get them to help you in a fight:
Stand like a doofus and intentionally take a damaging hit from the enemy, which isn’t so great against a boss or something that can stunlock you, inflict poisons/bleeds, etc.
Run the enemy in circles around your unresponsive thrall until you can get them to hit the thrall by accident, at which point the thrall (usually) joins in.
Technique #1 is potentially deadly. Technique #2 looks extremely silly and more appropriate to Yakety Sax than any soaring Conan score.
Now don’t get me wrong, I appreciate the passive default right now because you can run past things without your thrall stopping to fight when they aggro on you. But after over a year of early access + release, it’s high time to consider providing at least the level of basic attack and retreat functionality that WoW had fifteen years ago.
Failing that, can you at least extend the defense trigger to include you getting hit while your shield is up? That would assist option #1 since I’m not exposing myself to massive damage just to get my thrall to wake up and help. It also is a pretty clear indicator you’ve decided to engage rather than run. But right now I have to lower my shield and get hit or the thrall just picks their nose.