Don't fear the reaper
Reaper of Souls's plot isn't as terrible as the core game's - after all, what could be? - but it's still fairly dumb. I mean, I know we're talking about somewhat-trashy gothic power fantasy here, but at least the events of Diablo II felt consistent within the established world. Seven evils, Horadric staff, no one cared about Izual; pretty straightforward stuff.
Reaper of Souls turns the main game's "black soulstone" into a deus ex machina, more than once! The reaper Malthael's relationship with the angelic pantheon is just as groan-worthy as the "nephalem" garbage-lore. And the ending is so terse and anti-climactic, it's like it was picked out of a hat.
But hey, there's no Leah, so ... yeah, not as terrible as before.
My previous concerns about the trivial campaign difficulty were not abated by Act V. The final boss did succeed in making me pay attention to my health bar; but I still didn't die, nor did my companion. (Again, this was in the "Hard" difficulty.) And he dropped loot for above our current level! So I'd definitely call the game's definition of difficulty pretty suspect.
I know the whole point of Diablo is to continue climbing the loot ladder, and I've heard that the current game's Nephalem Rifts and Adventure Mode features are way better than previous iterations' Nightmare and Hell mode bullshit. But the early rungs of this ladder are unsatisfying and overlong. I'm not going to keep climbing on the gamble that it will eventually become fun.
Better than: current-day Diablo III
Not as good as: I remember Diablo II: Lord of Destruction being.
As for potential follow-ups: I lost interest in Torchlight II, and a brief try at Path of Exile didn't grab me... but I've heard good things about Grim Dawn? At any rate, more Borderlands is next on the schedule.
Progress: Finished the campaign on Hard.