Let me preface by saying that I am NOT a hardcore raider, nor will I likely ever set foot in a savage anything, let alone "Super Savage".
That said...
It's extremely beneficial to have this kind of content, so long as it doesn't take too much time and resources away from developing the rest of the game (and it won't, since much of it is tweaking values and whatnot).
Why? Because this kind of content is what gives an MMO "street cred", as it were. World of Warcraft has professional guilds with corporate sponsors who race to be the world first in clearing raids (and individual raid bosses, too) and this spectacle very much becomes an event unto itself that garners yet more interest in the game.
It also helps when players compare the two MMOs and trying to determine which they want to play: even if the player in question will never ACTUALLY enter Super Savage, they'll know for a fact that they'll never go without challenge in the game, and that's more important than you'd think.
Again, I'll never be a S.Savage raider, but it's good to know that there's a ball-busting, rage-inducing, professional raid team-destroying level of difficulty somewhere in the game for two reasons:
Firstly, if anyone tries to talk shit about FFXIV being "too casual", we can just say, "Oh? Tell me all about your synced Super Savage clear..."
Second, because it's comforting to know that such a challenge exists in the game if a player ever DID decide to rise to it. It's sounds strange, but there IS comfort in knowing that you'll never want for challenge in the game.
All of this adds up to S.Savage being a good thing overall: doesn't take many development resources and can only help FFXIV be taken more seriously as a solid MMO for raiding, which in turn means more income, which then means more resources for fun additions like PotD, Gold Saucer, Aquapolis, etc.