So there we were, storming this Lair of beasts and the best of us, stood on the edge of the cliff and fired at the great beastie in front of him, the recoil dropped him off the cliff and he died.
This is some kind of lore or are you talking about suicide shot? 
Because soldiers don’t fall of the cliff because of recoil. Or do they? 
Some video would be great.
I would say it was a bug of some sort, it was also my most highly trained solder too, he had a clear line of shot across the ravine in the cave system and fell off the edge of the cliff as he fired the shot.
I have never had that happen, I haven’t seen any recoil effects on weapons. What weapon were you using?
The closest thing to this, I have had happen, is using the firecat. Sometimes the line of fire arch shows it is clear to fire but it is really blocked. The nade hits something right next to the soldier and he wears the full affect of the explosion.
I cant remember the weapon, it was one of the heavier ones though, he was stood on the edge of the cliff and there was a clear view across, nothing at all in the view, and the recoil (if there was any) should have sent him further onto solid ground, the cliff edge was still there after he fell.
So looks like some problem with ground permeability, probably not connected with explosive weapon directly or any recoil. Just game didn’t saw that the soldier should stay there after shot. What I mean that shooting in that place with any weapon could lead to this death. It probably wasn’t related to that specific weapon.
My best character, in my longest game, Bang Aghhhhhhhhhhhh
Makes sense, prolly that ^
Good to know… moves all experienced soldiers away from cliff edges… 
May your soldier serve as a community service to us all. He sacrificed himself to let the rest of us know. RIP.