That is what I mean.
Just making them immortal like Wind Devils would solve most issues with the least amount of work for the devs.
I disagree. While this would solve a number of issue and make them more usable in crucible and a number of boss fights. The main problem is how difficult it is to apply the -rr and how short its last even after you have applied it.
The combination how slow you throw the mines, the activation delay, the small AoE range, tricky targeting and how short the -rr reduction last even after you got them into range of the mines(as even with face tanking many bosses still (inadvertently) move away from them).
It is only really useful vs large groups of mobs that run towards you and a number of bosses that are either immobile or stand still when you facetank them.
Considering that not all Demolitionist builds are designed to face tank the skill is just to limited in use even if they become immune to damage.
Can’t have everything. Some of those requests remind me of the guy who demanded that Inquisitor Seal be made to follow him around. 
Demo toys are clunky on purpose. You can’t have toons brimstoning the shit out of screens of monsters always at -100% fire/chaos res. Give them more health or just make them immortal and maybe increase the radius - simply change a few digits here and there. I wouldn’t count on devs rushing to the office first thing in the morning to work on new animations just because of this thread.
Maybe so, but a skill that deliberately misses seems like trolling. 
Like some of the others in this thread, I had been under the impression that the RR debuff stuck for a few seconds. I don’t think that’s all that much to ask for since it would at least make mines useful when kiting.
As for tanking, right now you have to drop the mines on the ground before the enemies get to you and hope that A: the enemies stand on them, B: an AOE doesn’t wipe them out, C: you don’t need to re-position, and D: you’re strong enough to kill everything within 60 seconds. That last one probably doesn’t mean much to most people on this forum, but for newer players taking on bosses it’s the icing on an already awkward cake.
Now maybe the mines are supposed to be powerful but unreliable and that’s okay, but right now I don’t know if that’s the case or if Crate just doesn’t know how difficult to use they can be.