Mines are useless now.
I would flog them at the next starport.
This is not true. They're just only really effective when used offensively.
Mines were originally envisioned as a defensive weapons, perhaps for traders and explorers who found themselves in combat. However, in the current implementation of the game, it is very difficult to score hits with them against a competent opponent defensively, as they will simply see you dropping them as you fly away and evade them.
However, if you boost at the opponent's vector and deploy the mines in front of them as you pass, if timed correctly and deployed at the right distance, it leaves little time for the opponent to maneuver out of the way in time to dodge them and they will usually strike the target. This method is known as "dive bombing."
This technique works best against jousting attacks (think frag mambas) as the enemy ship is boosting towards you, you also boost towards them and deploy the mines into their vector, then maneuver out of their way before they ram you.
I have videos showcasing mines in action in PVP with the reverberating cascade effect on my Youtube channel. Mines with reverb cascade are excellent for taking out prismatic shield tanks in ships that lack the DPS/hardpoint capacity to take them down otherwise with more "orthodox" weapons.
Me taking out a ganker Vulture's prismatic shield with mines over farseer:
Source: https://youtu.be/JQL36G4I2IM?t=490
Me taking out a ganker Mamba's prismatic shield with mines during a wing fight:
Source: https://www.youtube.com/watch?v=a0ewJQktVQY&t=1388s
I have done this many many times to other players but sadly I only have these recordings right now because I haven't cleared up any disk space for FRAPS to record more lol.
TL;DR mines are a very awesome, albeit misunderstood weapon. Used correctly, they are very effective at taking down prismatic shields.
P.S. The ion disruptor effect can be used to disable thrusters as well. You can combine mine launchers with ion and launchers with reverb to drop their shield and immobilize their ship at the same time, which will make destroying them much easier.