I am finding that EMP mines are quite redundant--it doesn't offer much to the game because their intended "larger vessel" targets, ie. Starships, are immune to EMP.
They cost 2X for disabling enemy vessels that can otherwise be destroyed by normal mines, and require 4K knowledge to unlock. It's not looking advantageous, unless the idea here is for EMP mines to disable enemy vessels, then allow defenses/etc. to pick them off, then I strongly suggest an AOE, or nullify the damage they do in return for a lesser cost, both knowledge and resource-wise.