I think it's a cool final boss. Actually fighting Sargeras is not possible for us. We're ants to him. So instead we mostly fight a proxy, with the goal of imprisoning the Dark Titan. I'm personally OK with this, and if it is developed well enough in the Argus zones it's definitely not much more out of left field than Archimonde, Kil'jaeden 1.0, or even Garrosh were in their respective expansions.