It's one of those games that never really seemed to find its feet, but I have a lot of fondness for Heroes of the Storm, especially now.
Look, I'd love to tell you that Fallout 76 was an Overwatch crossover where Soldier 76 shows up in a Vault and saves the Wasteland, but it's not happening. We're not going to see Omnics fighting Super Mutants, or find out that the Institute were behind the Omnic crisis, and we're certainly not going to see Talon agents battling Brotherhood of Steel forces. God, the fanfic writes itself.
The 20th anniversary of Diablo is right around the corner.
Heroes of the Storm is a Blizzard game which is essentially all about crossover between Blizzard's franchises -- you can play Tracer, The Skeleton King, the Lost Vikings, or Jim Raynor and fight Arthas, Thrall, or Tyrael.
Though most of Blizzard's games are set in fairly unique environments — fantasy for Warcraft, scifi for StarCraft, supernatural for Diablo, and so forth — there are times and places where these (and other) worlds collide in the strangest ways.