Fox, it is sad and, I am guessing, not true. Chances are, life with OW is not better. The only difference is that with you his feelings are numb and with her he HAS lots of intense feelings - lust, jealousy, anger... notice that these feelings come under the term "sin" in the Bible (not that I am very religious, but my point is that they are very strong feelings but they are not positive feelings - but for a MLCer they are better than numbness).
They are hooked to the drama, because they at least "feel alive" in the drama. They mistake "drama" for "purpose". They are searching for meaning and think that the "drama" gives there life meaning. But think about it - how long before the same dramas become boring, then the drama has to escalate and eventually they have to start to realise that this is not the sort of "meaning" that they were searching for.
If things were SOOO much better with OW, why did he come back to you AT ALL? If he was living his dream there would not have been a second of doubt, certainly not enough doubt to have him cycling back to you.
Fox, I know that you are finding this second BD very hard (maybe even harder than the first?) but you need to try to step outside of the situation and imagine it was happening to someone else. How would it look to you then? I'll tell you how - it would look to them the way I have described it - because I am that looking at it happening to someone else, and although I do not know you in RL, I promise you that it is the only thing that makes logical sense.
If he was unbelievably happy with OW, there would have been no room for doubt and cycling. Really. When you are your H were at your happiest points in your relationship, did you think "well this is great, but I would really like to be somewhere else, with someone else right now!" Of course not, because it was true happiness, not the confused and dysfunctional MLC version of happiness...