It's voracious ghouls, which are extremely tough in melee groups. Iirc they're vindictive(gets additional strikes when you miss/get blocked, this one I'm sure of) and enrage(higher crit chance when under 50% hp) and a base block chance. They would routinely one shot people. Actually do Lost City, at some point during it there's a harder part of the city where you're supposed to come back later, and it has voracious ghouls in there(note that it also has just ghouls, those are the easy type). So you can see for yourself, specifically it's on lvl 2 there's a path that lead to level 3 guarded by 2 voracious ghouls which you're not supposed to go to at that point, so you can see. Know that you'll have to fight like 4-5 at a time iirc, and there's also facehuggers(highly resistant mobs who drain mana on hit, but fairly squishy for melees).
You might be able to kill them fine mind you, I was just saying it's unlikely, but with a good amount of defenses and reloads, it might actually be fairly easy.