I think the sporadic movement is alright, but just he moves away from his initial location way too much and enemies that run away like this shouldnt exist imo. If they add sporadic / rapid moving enemies they should only move within a certain area/proximity. I think the sword he drops is alright as it gives a vit buff which is unique to swords and could be used purely as a vit swapout, but you are right I feel that it is more a lackluster bonus / item either way.
The enemies designed at the towers I feel are not really dodgable as they just stack a ton of bullets from multiple enemies (and they all do a lot of dmg aswell) is a poor way to design an enemy but I might just not have noticed a pattern of some sort to know if there is something to it. And the Keyper moving away while shooting the white projectiles is too hard to see with all the players covering the bullets as they pierce through. I agree it is poorly designed but it was a cool concept imo.
I also feel that the dungeons are made more for discords / thought out groups of players rather than a public closing realm group of players. The dungeons it should drop I feel should be more like mid tier stuff like manor / mad lab / davys etc rather than end game stuff as they take very long times to complete otherwise. the only one that i feel is sorta bad for this is halls. thicket / lod / shatters are fine the others i feel take a long time with a public group (nest/halls)