On my way back to town after completing a writ I ran into this creature, and it obliterated my character before I realized what happened. As far as I could tell there were no cues in the surroundings about the threat I was walking into, and the mob itself seem to sneak up on you. (I might admittedly not have been paying much attention as the other mobs were fairly easy).
I am not really opposed to having hidden bosses or mobs that are more powerful than the surrounding monsters, but when it comes so out of left field it's a death that feels very unfair. Some kind of environmental cues that you are walking into a tough fight and should stay alert would be nice, maybe some goblin bodies with blood around them and a description of how they were eviscerated by claws?