Just get rid of the 10 stones reward for doing random normals and put that into random vet.
Players running normal non-vet dungeons are running sub CP160 gear anyway and have no need for transmute crystals.
That would get rid of all the 1000+ CP players speed running random normals populated by beginners trying to learn.
Solution is way easier than that:
Make a separate 4DD RND queue.
All problems solved. All the DDs who don't care about roles go to that queue and get matched fast with other such dds with no need to wait 20 minutes for (fake) tank.
Now, the original holy trinity queue is left as it is. If you care about classic experience with tank and healer, you go there queue as proper role. There is no need to fake queue anymore, as you gain no advantages from doing so, just go to DD Rnd and that's it.