12 hours!? I don't know about this, devoting months of prep work for single raid...a 12 hour slugfest sounds like an overly drawn bummer...
That's the wrong mindset to have. The encounter doesn't take 12 hours to do. It just took them that long (closer to 11, actually) to do it first. When World of Warcraft was new, I was in one of the first guilds to take down Ragnaros in Molten Core. More than half the raid wasn't even at the level cap, and our gear wasn't even remotely up to par. There weren't many strategies for how to kill any of the bosses, because a lot of them hadn't been killed by anybody. We did it anyway, and it took us days. Days. It was a trial by fire, and the whole point was to figure out what to do and then do it. The article says these guys collectively died 1,606 times? That sounds about right. Obviously, when everyone else tries this raid it will take a lot less time. That's how these things work. Later on down the road, when you're level 28 and you try this raid out with friends, I bet it will be a cakewalk and take you a couple of hours.
TL;DR this doesn't apply to most people who will play Destiny, only the crazy ones.
"Though it took more than 10 hours to deconstruct Vault of Glass, Primeguard figures a team knowing exactly what they were doing could finish it in two or three hours."