Boss Drop Rate

I don't think it has anything to do with aggro; I've been bringing a Kanna mule as a binder as long as I've been soloing. I've hit magnus with the teleport before, and the "aggro" notice on the boss notification bar routinely says my mule is "the most threatening enemy."
Terebii; has gotten quite a bit stronger recently, and I had him bind for my last two runs since Kanna's are so broken atm, and it didn't hurt my drop rate. He was making sure to use smite outside of the blue zone to reduce the damage dealt, however. Magnus considered both him and my Kanna mule as "the most threatening enemy" several times throughout the run as well.

The boss aggro bar is super broken, it would occasionally forget my Bishop was even in the map and the box would glitch up ;_; but that can't be the reason then. I imagine there probably is a threshold that you have to pass in order to be added to the 'total' drop rate thing, but how much that threshold is exactly isn't going to be particularly easy to figure out haha

And I'm not sure exactly how long ago this has been in place, iirc it didn't work like that when I used to run Horntail in 2009 ish but I'm pretty confident it did when my guild started doing Cygnus runs in 2012 or so. There have been several 'general update' patches in the past so I wouldn't know when exactly it was adjusted but it's extremely noticeable with Chaos RA (and Vellum in particular).