May I suggest two things to make <C-U> and <C-D> more usable?

1. Set 'scroll' to a value you're comfortable with, so that <C-D> and <C-U> move fewer lines.

2. Use a plugin that shows a scrolling animation when you use <C-D>, <C-U>, <C-F> or <C-B>. I use vim-smoothie (https://github.com/psliwka/vim-smoothie).