hit HR 50 yesterday after doing the Kirin quest, and I think I will stop there. I think that I could easily be drawn into getting HR 100 if there were more obvious goalposts along the way. I enjoyed stuff like the double tempered Bazelgeuse; I wish there had something like that every two or three levels, or at least let you know in advance 'hey, this is gonna be the new tempered elder in 5 hr levels, start thinking about how you are going to build for it', so that it didn't feel as aimless. I know that the investigations are kind the like, randomized version of assignments, and potentially there is a lot of fun to be had there in doing weird combinations and stuff, but the way they come in randomly isn't super fun for me and I don't love combing through 200 of them all the time. also I think i would be more inclined to continue playing if i had a steady crew! but the two squads I had joined seem to be totally dead now.
that being said this game was fucking excellent and i'll be happy to jump back in if they add new monsters or modes.