Imagine thinking Preach’s fanbase is “the vast majority”. Most people are just going to enjoy the expansion when it comes out and be happy with an improvement.
Torghast will be “done” once you get your legendaries from it.
And again, it is important to note that the third chest is not something everyone is expected to earn, it is a prize. The first chest is a “freebie”, the second chest requires a bit of elbow grease, but the third chest looks to be designed for hardcore M+ers.