I feel that a different concept form XI would get the danger across more (as much as they can without Gameplay/Story Segregation or sacrificing player convenience). Alternate Universes showing what will happen if we failed at any point our didn't exist (Say Ifrit. Titan and Leviathan tempered and took over the starting citystates. Nidhogg battling Garuda and Ravana for control of Ishagrd. Garlemald managing to conquer Eorzea etc.)

Given what we (don't) know about the Warriors of Darkness and that Hydaelyn confirmed the existance of paraellel worlds (and that some still remain IIRC), I think that 3.4 will be a great jumping point for this concept