He is "dead" sure but his essence remains otherwise there wouldn't be any Sha now would there.
It is implied the Titans wander the cosmos as a whole to bring order to chaos at any cost, some of them seem to be dispatched to scout but otherwise it was never stated that they as a race are splintered across the universe and even if not all of them were on Azeroth we know for a fact, that the Pantheon was on Azeroth, they imbued the Dragon Aspects with a portion of their power after all. The demons of the burning legion pretty much follow the strongest and over time the old gods could sway many demons to their side. I mean even Azshara and Illidan were able to convert demons to their cause.