This is a tactic I use whenever possible. Two well-placed shots at a Hunter’s head with the Magnus (the first knocking off the armour) seem to destroy it. It seems to work on all classes.
I was just curious as to if anyone else does this, or has done it unintentionally at one point.
I’ve heard that the head was a weakpoint but it’s extremely difficult to hit. I’ll need to try this next time 
I killed one with a .50 cal shot to the fuel tank today as it was walking away. Well… it was walking but stuck under a shed roof so it couldn’t turn or defend itself… maybe it doesn’t count. First time I’ve managed a one-shot though.
I actually believe that I’ve had a hunter commit suicide when it saw me. I was inside a kitchen when it fired a shot at the fusebox outside. Instantly blew itself to bits.
I have seen that a lot. It happens if you are inside a tight spot and they fire missiles point-blank at you and hit something close by. Yesterday I was at the bunker full of machine power cells doing that mission and after clearing the exterior of the facility and blowing up the lorry, a hunter went bonkers inside the closed door and kept pumping missiles at the door - or maybe it was one of those missile equipped runners? Not sure. There was a red laser designator shining through the door. I eventually opened the door and took cover and popped out 2 to 3 times with the shotgun to take down a hunter and when he went down and I went inside there were 2 hunters and 2 runners destroyed in there and I know I definitely didn’t do that.
So, yeah, some wonky AI in the game that could do with improving.