Well the first thing I have to say is....I feel bad for talking about them without someone from their raid group being here. I don't hold any ill will in my heart or mean to cause any drama with the words I say here, but from what I can tell:
Just like A3S when it was brand new, with a Paladin in the party each and every single person was/is walking on pins and needles with the best equipment to get the task done. I'd wager if each person were to make just two mistakes (whether it be weaponskills, cures, defensive cooldowns, placement and positioning, etc,) they will have caused the group to fail. It requires nothing short of perfection on every single attempt to ensure that it gets done, down to the very distance each person runs during X mechanic; which brings me to my next point. From what I can observe in videos and the stream the tanks have had to stay in their DPS stances for more than 80% of the encounter. That means 3.5 legs, the head, and all adds were dealt with while they were at their most vulnerable in order to complete the floor. I admit, they did switch to tank stances intermittently but a large....and at least from me, I mean a disturbingly large majority of the time they weren't in tanks stances. Throughout most of their attempts the tanks lost aggro to one another and the healers at times which caused the group to fail. I'd say the amount of wiggle room with a PLD/WAR right now is thinner than a human hair as compared to WAR/DRK. They're in the same position Zdenka and Blue Gartr were in with A3S. Too much time invested in attaining absolute perfection to give up.
Furthermore, I'd wager if you watch DRK/WAR setups complete A4S the entirety of the encounter will seem more structured, more predictable, and less strenuous to every player. While it might not seem like it, that's what the community is caught up on when regarding clears with PLD. It requires perfection in every sense of the word for it to even be possible....and that's with a Warrior (who brings the best possible toolkit to the encounter) as the other tank. I shudder to think of how DRK/PLD would perform.
Can it be done is the question everyone is asking.....this is proof that it can be.....at a later date (week/s at best and month/s at worst,) with an exponentially larger learning curve and performance demand. I can't help but commend them for beating it even just once and they provide the sort of group dynamic everyone should strive for when raiding. You can tell they care for one another, you can tell they're all nervous, you can tell they don't want to fail each other but they're ready to just keep trying and enjoy living. I just wish it wasn't so stressful for them.