I wish this game actually felt like a sequel to Diablo II instead of its own thing. I just feel like Jay wanted a "clean slate" after the fallout of Blizzard North's collapse. It's a slap in the face to all of the fans and I still have bad blood about it. I know it's their game, but Blizzard lore is legendary in itself.
While I also wish that D3 was more of a direct sequel to D2 (I loved how the Barbarian was supposed to be the same one originally and was disappointed they backed off on that), I'm not really sure Blizzard's lore was ever very legendary for the Diablo series.
Speaking for myself, I never felt particularly attached to "Sanctuary" as a cohesive world, and I never felt like there was much back story but for a few characters (like Tal'Rasha. But, who was Sigon? Trang-Oul?).
That said, I do feel like D3 was a missed opportunity to develop some sound lore, and the reconning the Dark Wanderer was just a shame.