I've tried all kinds of values for r_dirshadowmapratio1 with no visible result, while r_dirshadowmapratio2 did show visible results as you can see below.
After testing and experimenting for some time, I've figured that if you enter r_dirshadowmapratio2 0.04 in the console, Duke's shadow and every other shadow that's closer to you, becomes much higher res and much sharper than default.
The downside with this is that at a certain distance, the shadows look as low res as they do from default.
This setting here only applies to the closer shadows.
If you increase the value from 0.04 to let's say 0.09 I've noticed that the further shadows become more detailed while the closer shadows become less detailed.
So 0.04 is the point that I found to be the best for me.
Try it and you can experiment with various values like 0.01 or 0.1 , 0.2 and up to 0.99
Here's a comparison that I've made for curious people.
It's not much but it's something.
If you like it, use it and enjoy...

