Try targeting at the feet, in crowded situations I have had an issue with the right target being selected. Again look at the combat highlight, if the circle under the target highlights, you are targeting the correct thing.
For ranged attacks, you can click on anywhere on the model and it actually can make a "non-visible" target "visible" as maybe the bow arc couldn't hit the target at the legs, but if I move up the body to the head it can make a clear shot.
I will check out the screen shake in a few to see what you are talking about with eldritch blast.
Ultimately these are all work arounds, and if you are having an issue unique to your interaction with the UI then bottom line it doesn't work for you. Just trying to suggest things I do. I haven't had the feelings of difficulty that you say, but maybe I am less impacted due to being less particular.
