How, pray tell, does one miss the intro quests to Hyjal and Twilight Highlands? I can understand all of the morons who abandon quests and forget where to pick them up missing the battle between Alexstrasza and Deathwing, but you can't begin questing in Hyjal or Twilight Highlands without doing quests where you see him.
And then there's the dozens of different quests throughout the 1-60 experience where he and the Twilight's Hammer are mentioned.
And how does Cho'gall not tie into Warcraft 2? Or the entire Dragonmaw Clan?