The heck... mine says 10W while idle! How??? I'll take 1.5W over 10W any day.
Sleep: I don't have working sleep! Surprise surprise. It never goes into S3 sleep and when I wake the laptop, the screen stays black with the backlight on.
Also, @ mods: is there someplace we can make a "device support" thread? This is becoming a catch-all thread for the XPS 15 9570 4K and it's a little odd.
10W while idle? That's way too much damn. Maybe something was going on in the background?
I use to have the same sleep bug as you but after fixing other things like the combojack and 3min dark display bug, when I try to go into sleep and wake it up it either stays in a black screen no backlight, or crashes and reboots lol.
I'll attach my Clover folder here in a few minutes in case you or anyone else wants to use/test it. Warning - i just changed my SMBIOS to MacbookPro15,1 from MacbookPro15,2 as 15,1 seems like a better fit and I thought that would help the package power decrease - right now seems like it hasn't made any impact positive or negative. To be fair the CPU seems to be scaling properly to load on both SMBIOS - it reaches and stays at as low as 800MHz which is much lower than Windows, but for some reason overall package power is still higher (Windows: min 0.5W whilst macOS: min 1.5W - both data figures from observing Intel Power Gadget)
Edit: To fix combo jack you need to have the verbstub kext (in attached clover folder) and run the combojack installer script (you can find it in the downloads of Dell XPS 15 9560 High Sierra tutorial)