EC: two healthbar setting changes to make
First change is to increase the number of healthbars shown. The default "10" may make sense at lower resolutions, due to limited screen real-estate. Higher resolution, can have many more bars. 20 allows you to pull 20 bars that you are tracking, and 20 that show up in the dynamic mobiles list.
1. In healthbarmanager.lua
--HealthBarManager.CappedNumServerHealthBars = 10
HealthBarManager.CappedNumServerHealthBars = 20
2. If you have the mobiles bar enabled, right click on it, and make sure to disable distance sort, if you don't need it. In my case, I find that adds client lag when many monsters are on screen. Sorting can also lead to targeting mistakes as the list of mobs can change in the process of clicking.