Volume II book 7 was entirely solo as were the first few chapters of book 8 so it was quite a surprise when book 8 chapter 3 A Relic in Lumul-Nar turned out to be a very challenging 3 man instance. My Champion Throg was lucky enough to get the help of another champion and a minstrel from our kin but we were quite unprepared for the difficulty level of the instance, which I later discovered is called "The Hall of Mirrors". After many wipes and much consultation we did eventually overcome the first boss which required positional tanking and carefully timed corruption removal but it was getting very late so we didn't manage to complete the instance. You can read a fairly good walkthrough of the instance here. The key to the first boss is keeping two buffing matron wargs apart and preventing them from healing by removing a 10s corruption (buff). For reference we had our minstrel kite one matron while two champions beat on the other and that eventually worked.
These kind of tricks are more common in 6 man content than in 3 man. Indeed tough 3 man content is all the more challenging because you are unlikely to have all of the classes you would like and you need to figure out a way to make do with the three players you have got. I am looking forward to giving it another go but it may be a while before I can get a suitable group.