wait am i not supposed to be mining the third obelisk layer before even going to santorini?
In theory, it is entirely possible to complete most, if not all current content without mining the obelisk at all. In reality, that route isn't particularly well balanced at the moment, so mining first is the preferable route.
What I meant was that once there's more content in other directions, the obelisk will likely be made harder than it is, so that you're more strongly encouraged to go other places, find upgrades, then come back to deal with it. But there's not enough content for that yet.