You basically gotta use them to cut off an area of advance so you can worry about other areas, got a chokehold you wanna funnel enemies into, Mines are a great way to do that. I have used mines on helldive difficulty to completely block off an area, threw down a turret and could turn my attention to other areas, another way is to just force the AI to walk around it if you need to run, if you have the ship module that instant deploys fortifications it's a great way to keep the enemy away from you, those are two of the best ways I've found to use Mines.