[Q]

I basically agree with you Geoschmo that mines are too powerful in the early and too weak in the late game. I just think the difference is not that enormous.
The minesweeping components to clear 100 mines cost alone 10000 minerals. Therefore the cost to build and more important to maintain a sufficient number of minesweepers can be important. And if you find this still too cheap, it can of course be modified and increased.
The changes MM made in the Last patch with new mounts/damage types gives me hope that the mine suggestions could be realized too in a future patch if we continue to ask for it.