I've been tempted to try multiple minelayers and then using coordinated order to litter the table with mines. But its because on cheap sacrifice can blow up multiples mines. I've used HoloEchoe, and Nasmats to take out mines/crazy koalas for virtually no cost.
And you opponent has cleared your Koalas and Nasmats at the same time, so it's not that bad of a deal. I agree that you want to make it as costly as possible for your enemy, though, so you have to place the mines very carefully if you intend to invest a lot of points/orders into placing them.
Minelayer efectiveness varies from table to table and from army to army: mines can be a nuisance or terrifiying depending on who you're playing with. Some get meh, some get rekt. Sometimes my farzan minelayer have died with 2 mines on his backpack while doing his job. Allah be praised! If laying a mine makes an opponent burn 3 orders and take the life of a warband, it will be a better trade than killing some dogged or NWI troop when he/she is aiming to score objectives. But as a rule of thumb, minelayer protecting your link team and making your opponent to take difficult decisions it's always good.
In general I prefer killing people than making them unable to fight via E/Mauler. Isolated models can still ARO and can be fixed. Dead models cannot.
Well, it's relative resilience of targets to different things that matter. Some things are way easier to immobilize/isolate with E/M than to kill, especially with Haqq who can also remove support pieces well enough. Besides, triggering your mine usually means some overextension. If opponent needs to bring repairing model on the spot after that, it's possible he could very well be welcome to do so.
