It took me 9 infested mines to find 15 black cores, which looking back doesn't seem that bad except in the meantime I had to constantly break down and swap crafting stations. Not terrible, but not ideal, either.

Core counts for the 10 mines I've completed are 4-2-1-0-1-1-2-1-3-1 - first one was very lucky, without that I'd still be out there looking for mines.

Also, I finally tried the magic, and it's really fun. The frost staff works pretty well against seekers, and the staff of protection seems essential to survival as a mage.

I'd like to see some more higher-tier balanced foodstuffs that give equal amounts of all 3 stats like the raw Magecap, for example a mushroom platter with Yellow Mushroom, Magecap, and Jotun Puffs that gives 40/40/40 or something, and just more of the balanced food types in general, along with some earlier access to magic foods like I suggested earlier.