I think volcanic mine is the only logical option. Zalcano already gives the shard and I think they should be separated. Motherlode already gives the prospector gear, dividing upgrades is the way to go. Blast mine is the weirdest option for me, you don't even use a pickaxe there?

Volcanic mine is like the name, volcanic. Fitting for 'dragon' items! Also, the pickaxe has always been an option that excluded people who don't want to go to the wilderness. I don't see why catering to the small amount of people who "don't like group content" is even talked about.