Warcraft 1/2 -> Mannoroth enslaves the Orcs
Warcraft 3 -> Mannoroth is killed by Grom Hellscream with full cinematic complement
WoW Cataclysm -> Mannoroth is final boss of Well of Eternity
WoW Warlords -> Mannoroth is killed by Grom Hellscream with a full cinematic complement...again
WoW Warlords patch 6.2 -> Gorehowl to the head with his blood spilling everywhere was merely a setback.
Jesus, there's other Pit Lords in Warcraft lore, couldn't they have shaken it up a bit and at least given Maghteridon an appearance, who would have now seen Mannoroth dead and taken up his place, which he takes anyway in Burning Crusade (further in the future)?
I get it, Mannoroth is in a way the root of all evil which heralded the beginning of the Warcraft saga, but he died TWICE in two timelines already to the same weapon weilded by the same guy. Don't tell me we'll see Grom do it for a third time in an act of sacrifice or some bs.
Edit:
The finality of the cinematic is just....final. It's also symbolic. Garrosh even says: "Times change". It's the theme of the entire expansion. "Times change, this is gonna be a different story, hold on to your hats." Now it's what? "No actually, it's the same story but instead of going A to B to C to D we went A to b to B to C to D."