People need to learn to have a better anti-mine strategy.
Basic mine strategy:
1) Do not have any of your fleets that could possibly jump into/be jumped on have the engage in gravity well fleet order. Hold position, or possibly short range attacks only. More micro-managing, but at least your fleet wont jump into a system and get themselves blown up in an attempt to wipe out a constructor.
Tried it. Cap ships decided to bombard the planet anyway, and went stampeding through a minefield to do it. Only thing I could do was mash "Stop" as fast as I could and hope that it worked in the lag. That was despite having scouts tagged to follow them, so they had detection moving with them.
2) Scouts, scouts, and more scouts. Scouts + (battle cruiser/dreadnought capital ship) or starbase (vasari's mobile base is best) or carriers are the most effective way I've found to defeat mines. Get your scouts, turn their fleet orders on "Hold position" and move them near the mines which will uncloak them, next the other ships further in the background can take them down with beam weapons/fast firing weapons. Also if the mines detonate on the cruiser when it approaches (if it approaches too closely, Advent homing mines in particular) it can take a couple of hits without being obliterated. Plus, you get 5-10 xp per mine, and if the mines are numerous enough.
You can do this, but it takes a very long time to clear 500 mines, and it's absolutely nothing resembling fun or compelling gameplay. It's mind numbing grind.
3) Never jump your primary fleet in first, always send in a scout before jumping in to a) decloak mines so incoming fleets have some sort of chance, and make sure the jump path is clear.
More strategy peeps!
Doesn't work when the grav well entrance itself is covered in mines. Scout comes in, ships come in, ships still blow up.