Do the sewers now drop all vet 16 mats if you are vet 16?
No idea. In Wrothgar and Hew's all materials scale to your crafting passives. So if you have 10/10 blacksmithing, everything will be Rubidite. If you have 10/10 enchanting, potency runes will be either V15 or V16 (though they still favor V15).
You can have a situation where a character will get some materials at V16 and others at 1, if they have no passives for it.
That said, I do not know how the sewers work now. I haven't been back to the IC since... last year sometime.