I just finished this on my 60 Guardian equipped with level 39 yellows (with +40 power nourishment).
Maybe they fixed this (don’t remember if they were level 59 or 61), but it was doable. It was my first time doing the mission and it took me a while to realize the risen respawn endlessly until you kill the Veterans, but I could safely ignore the trash and go straight for the Veterans until they all died. Is it really that difficult? I can see why other classes with less healing and condition cleansers would have problems though.