So, I’ll take a few moments to say that after viewing the cutscenes on YouTube, that I am quite content to eat my fair share of humble pie in regards to Diablo III’s story direction. My other points stand, but I can’t gripe as much about the storyline. There is one little point I’d like to have an answer for and I'd like to see if anyone has some clues for sating my curiosity:
In Act III, you defeat Mephisto and shatter his soulstone in Act IV, which will apparently prevents his return.
In Act IV you defeat Diablo, and in the ending cinematic, the player shatters his soulstone which should apparently prevent his return.
In Diablo III, Diablo makes his return and wrecks the High Heavens before being cast down by the hero.
So, how does Diablo manage to escape being oblivion after being slain in his home plane of existence and having the soulstone he’s bound to crushed beyond repair?