Oh no, i don't think it's just you. All the mines seem too powerful vs the AI's ability to deal with them.

In my opinion, the problem with the mines isn't the power of them, it's their target priority to the ships, and the kooky detection system. Unless this is a bug, whenever my scouts detect the mines, the mine becomes targetable for a second, then becomes untargetable again, and switches back and forth.

This screwed with my attack order on the mines, as the ships switched targets as soon as the mine became untargetable. They switched targets to a light frigate halfway across the grav well, and my ships promtly blew themselves to pieces chasing their new target.

I did get my revenge though, by placing a line of mines and a colony frig at the other end of the system. And you know how much the AI loves to target those colony frigs...

So, unless it's a bug, I did something terribly idiotic, or there's some special way to get rid of the mines, I'd reccomend changing the reveal on the mines to a permanent detection, not a flickering one, and make the mines on the top of every ship's target priority list.

If this doesn't make any sense, please correct me.