Every other raider is workaholic now. Makes sense.. they sure raid all the time!
You buy one mine, yeah you just take the other. But that's not an easy fight if my memory serves well. Was a long time ago.
BUT the one you purchase is better. Was better. I don't know if still is. Kahil comes with gold ore, the other didn't. Definitely start with Kahil.
Workers doesn't matter, it's not like Zapin. Just shovel in scum (if i recall correctly). It's the guards that matter but ONLY if you send your own NPCs. Use Sera Guards.
Another thing. You cannot take back miners but you can transfer them between mines. Run 1 mine at a time so when that one is done you can transfer all the miners to the other. This way you won't lose twice the amount of people

No biggie if you do, just a matter of how many slavecapture grind you wanna do.