The only real thing that I actually seen to work in diminishing the staking was the fract lvl 39 deb (mobs explode after death) combined with dredge fract transforming even the trash mobs into dangerous opponents if not dodged properly and when we stack… can’t really dodge them all; combine that with zerk gear and you will see people die without a bit of toughness and vita.
So basically instead of doing pointless nerfs, the easy and reliable solution would be to remove the one shot kills from mobs so tank geared players can actually feel a difference between zerk and ptv (in terms of survival) and add more effects similar to those encountered in fract.
Although what concerns me is that some classes feel useless inside dungeons, like engi (casual and average players) and ranger. So at least be happy you have a guard or you would have a hard time even to find a group.