"I hope the final boss of the expansion has the dragonriding theme, they've set it up as the expansion's main theme so it would fit really well and be a great sendoff for-" Blizzard giving it to the penultimate boss instead: "My goals are beyond your understanding."
I can see why, to an extent. this fight is fought above, out in the open. *everyone* in the dream near Amirdrassil sees it. *everyone* sees the sky rage in fire.