It definitely used to be faster when you could sell the sorcerer’s skulls, now I’m not sure.
Regardless, you can still get them from their original place at Bin-Yakin’s Seal, and you are right it is overall faster to do that, and they have higher durability than Obsidian tools.
The only reason I would get an obsidian tool, which I have yet to try since the update, is to apply an Oil of Bounty on them, and use the Repairing Grindstone to get the most value out of my Fragments of Power 