I'm still having fun with it, but I'm also on the opposite end of the spectrum from those who prefer stuff like PoE. Diablo IV is exactly what I want out of an ARPG. It definitely held my interest significantly longer than the D2: R, which just isn't what I want out of these games. I had fun with my initial playthrough, took a break to play a bit more TOTK, Age of Empires IV, and Two Point Campus, and started my 2nd character about 2 weeks ago.
I'm sure it got a big drop in players since launch, but what game doesn't? 2 months in the game industry might as well be an eternity, and if it's not a Nintendo release I'm sure you could find decent deals on anything in that time frame.