Originally Posted by Emissary of Justice
During the talk with Nagato, it was stated that the technique cannot bring back those who've been dead for so long or else Jiraya would've been revived. Hell, I'm pretty sure he'd have brought back Rin if that were possible. I always got the impression that Madara's expectation of revival was an overestimation as a result.
I'm pretty sure there is a correlation between the amount of chakra needed to revive somebody and the amount of damage/decay the person being revived has taken. The people nagato killed either has their souls ripped out, died from chakra exhaustion (kakashi), or from some sort of physical damage from certain paths like the animals or mecha one. For the first 2 it's just a simple matter of restoring their souls and a bit of chakra to revive them. For those physically killed, the jutsu provides just enough healing to close the wounds up so they don't die again as soon as they're brought back.
For someone like Jiriaya, the technique is pretty much useless. At that point the guy had been a corpse for over a month. It should have taken a lot of chakra to revive him, and heal his body back to a stable state. Assuming he could J-man was still at the bottom of a lake deep enough that Kabuto couldn't even reach him. I'm pretty sure he'd just drown again.
Although you do have a good point about Rin. It is a bit of a plothole. Although to be fair Kishi hadn't unleashed the Tobi=Obito reveal at that point, so he really couldn't have Nagato do anything related to Rin in a relevant way until he did.