Now, I dislike the mechanics of the Sartharion with three drakes up fight (don't stand in this, run away from that, are you standing in that), but that doesn't mean that it's poorly designed, and I think it does exactly what Blizzard set out to do. It creates a means for anyone who can get 10 or 25 people together to experience raid content while simultaneously giving guilds that like challenging content a way to pursue that without making some content simply inaccessible. There was a lot of complaining in the past that superlative raids like Naxxramas 40 and Sunwell Plateau simply weren't accessible to the majority of raiders due to their difficulty. With hard modes, raids can choose to do this content at its most basic setting and get to experience the content, or they can opt for more difficulty and get better loot and bragging rights.
Honestly, I don't really see Lightsnight's problem here. But I am glad that Valnoth confirms that not only are hard modes not going anywhere, but that they will continue to provide some of the best loot in the game. Now all I need is for them to remember to put a 2h weapon that can be used with Titan's Grip on a hard mode boss next time around.