We're considering a more holistic approach to skillers of a way to turn off "direct" XP rewards (from quest completion, challenges, etc) for certain skills via Nastroth, rather than continuing to modify individual content's rewards.
Here's a link to JannaMechanic's latest proposal for direct XP blocks:
https://www.reddit.com/r/runescape/comments/pvcjsa/comment/hkubst1/?utm_source=share&utm_medium=web2x&context=3
It's buried in a reply to a thread where there's been lots of discussion around skiller/pure QoL (that's gone far beyond the original thread topic), as I thought you might find that an interesting read if you've not already been involved. :)