I think right now though Reno decks are running far more anti aggro cards then Jade decks. I think it is very possible that if you were to tune a renolock deck as well as you could vs jade, and you did the same with jade for Renolock the jade deck might come out on top. But I dont think it is a given. There are a lot of great cards out there not seeing much use because Reno decks have like 10 or more slots dedicated to anti aggro tools. Even for this meta if you could safely run Rag, Cairne, Sylvannas, and maybe one more big late game card that might be enough to just destroy the jade decks in their current form. The problem is you can run one maybe two before you are just giving up huge chunks of of %s against the most common deck, aggro.
I think turn 5 kills before MSOG was fairly rare, requiring basically crazy nut draws and your opponent playing nothing. With pirates you could have your opponent kill several things, not draw perfectly and still possibly like reaper them on 5 for the kill. Looking back on old face hunter (Not the undertaker version), going first with the absolute nut draw unless your opponent clears zero minions and heals none of the damage you wouldn’t kill them by 5. Not saying much since you be overkilled on 6, but this is quickest meta I think there has ever been.
I looked into trying to build a deathrattle priest singelton, and as of now you are pretty much right. There are only 7 viable DR cards unless you put in techy stuff or things like harvest golem. But if they add 1-2 priest deathrattles, which is likely considering the quest and 1-2 decent neutral cards then the deck wouldn’t be out of question.