I completely agree with the OP. Most of the bosses are incredibly easy and have barely any mechanics at all. It should say something that I often can’t tell whether I’m fighting a boss or a trash mob.
My hope is that in future more mechanics, interesting ones, will be added to bosses. And I would also like to say that spawning 20+ trash mobs is NOT a a boss mechanic, not an interesting one at least. Most of the bosses that have any difficulty to them seem to have be been artificially made so by using this trick. Of course, there has been a few good bosses, such as lieutenant Kohler, so more of these, please!