Driver 1.8 has been all they have given us for going on 3 years now. I myself do not expect they will ever offer anything better. I doubt if there's anything that needs improving that can be improved. It's a rock solid driver and I doubt if they get complaints.
Updated drivers are for bug fixes. And you can't expect better latency with any interface that uses hidden buffers. You need to go up there to brands like Motu & RME. It is what it is, a budget interface for hobbyist.
The RTL does not change for me on any system. I have used it on many computers,, W7, W8.1 and W10, Old duo cores, Gaming i7's... 4 Gigs RAM- 16 Gigs RAM etc,, and the performance has never changed by more than a decimal point.
It doesn't owe me a cent at this point, 3 years is a good time to think about my next upgrade. It won't be another Focusrite. Nothing against the company, they are great, but I want better pre's next time, these are shabby. And better RTL might be worthwhile someday. Right now it is not hampering my set up as everything is direct monitored.