there are 2 advantages of having own mines: you know where they are and you can defend them. but right now defending is risky as you might lose a lot more than the potential attacker. thats why there are that many unguarded mines. i think that attackers should get 10 m3 less loot. that is when the mine or harvester is full they get ~70 m3, 10 m3 is left in the mine and the rest is wasted. and if theres less than 10 then the attacker gets nothing. this means people unloading their mines every 10h or so would be safe from looting.
You really should read the last update.
- Combat balancing: when looting mining modules / station cargo bay resources, 20%-30% of the resources gets wasted in the looting attempt.