Totally with you Alexbob. This box did not mesh with my partner's and my playstyle at all at the time, so we quit playing the game for a month. It was Cair Andros that did it for us, too--the frustration sort of built up throughout the box and then having Cair Andros as the capstone felt like a slap in the face. We eventually came back to it with two mono-Tactics decks, crushed it, rolled our eyes, and moved on.
There's definitely light at the end of the tunnel--the Against the Shadow cycle isn't nearly as hard as the Heirs of Numenor box, and it has a few real gems of quests in there. The Morgul Vale is pretty tough, but somehow it's easier to accept since it's at the end of the cycle rather than the beginning. Even so, it's not as frustrating as Seige of Cair Andros, in my opinion.
If you get too frustrated, you can just skip it and come back to it later. I'm a completionist too, but I won't tell anyone if you don't.