Frost Rune Guard

Very unusual, this mob has no situational awareness. What I mean is, he is not social. If you have two standing right next to each other, you can safely pull one without adding the other. On the other hand, they do have a slightly-larger-than-normal Aggro Range.
As to damage... their is not all that damaging, but they are fairly strong on melee damage, so it is a very good idea to use skills that prevent them from closing to melee range.