For the future of WoW universe, yeah, but for the sake of discussing how powerful someone / something is for killing time, no. There is quite a big difference in power requirements between blowing up a solar system and blowing an entire universe in a single move :P
He didn't die on Argus, though. For all we know, it might be possible that Argus' power only works on the planet Argus. We were still pretty far from it when the ship exploded.
Right, while I wouldn't completely rule out the chance that Blizzard decided to throw away logic and just create something cool sounding, I think it's possibly flowery language as well. If a newborn Titan (whose soul was tortured for ages) has enough power to destroy the universe, Sargeras wouldn't even need to create the Burning Legion to begin with. Back then, he didn't know of Azeroth and was only thinking about remove the corruption of the Void from the universe by destroying everything.