I think the Mystical is a gorgeous pack of cards, but it's a bit difficult to wrap my head around some of the images.
It may sound dumb (probably is), but Lenormand is a complex system in some ways. Like if the book is open, or the coffin isn't draped on one side or the clouds thing we were talking about yesterday - there are so many visual cues I seem to need to wrap my head around to get the combos - plus the playing card symbols - without those, I'd probably forget who's where in the courts. I learnt to read in Europe more years ago than I care to admit, but have only taken up Lenormand again fairly recently, so I need to relearn a whole lot. Combinations especially, because that's the key to reading it.
On the particular issue of the 8th house, I have seen people make good arguments that it's not about sex (Dave Roell had an essay on his site, it may still be up), or it's only sex on the astral plane, and that you can cover intimate relationships in 5 and 7, but I'm not so sure I agree. I tend to see a lot of other people issues in 7-12, and a lot of personal in 1-6. Granted, that isn't a hard and fast rule, but it works pretty well. Where would joint values go if you didn't put them in 8? Maybe in 7, to a point, but money usually represents so much to us humans that it deserves that 2/8 axis - what's the thing that most marriages break up over, after all?
Granted, astrological correspondences are a little more set than maybe tarot would be, but as a friend of mine once said, after enough study, at some point it becomes a democracy of one deciding which you're going to use.