The targeting of these two schools are both very precise, but the list used is that of Koto Ryu. It could be argued that Koto focuses just as much on pressure-point striking as Gyokko does, as there are a number of kata which strike to Kimon (not bone), U Sai (not bone), Matsu Kaze (not bone) etc... In fact, when teaching Koto Ryu, I usually make the point that although the kata themselves are (seemingly) a lot simpler than, say, Kukishinden Ryu, the principles of timing, distance, and exact targeting found in the system make it a far more difficult art to truly master.
The reason the Koto Ryu list is used, by the way, goes back to the origin of Koto Ryu itself. Sakagami Taro Kunishige was the head of Gyokko Ryu at the time, and according to some theories had found that the battlefield had changed so much that Gyokko Ryu was no longer as effective as it had been. He was introduced to the knowledge brought from China via Korea by Chan Busho, and applied his own understandings, developing Koto Ryu. From that point on, Koto Ryu and Gyokko Ryu were taught together, to the degree that the Gyokko Ryu used to train their techniques against the "attack" techniques found in the Chuden and Okuden sections of the Koto Ryu scroll. Gyokko Ryu then adopted the superior knowledge of Kyusho from Koto Ryu, in much the same way that Takagi Ryu took the Kukishin weapon systems (and Kukishin Ryu took the Takagi Ryu jujutsu) after those two arts came into contact.
So the two arts are really "sister" arts, or, as I see them, complementary arts. To only train one is to miss a big part of the picture, so to completely separate them would not be understanding either.
One thing I will say, though, and this is probably not the safest forum section to bring up this story, is to go to your comment about "caus(ing) blinding pain AND knock them off balance". Kyusho often just don't work that way. I wish they did. But they don't. Story time...
A number of years ago, Ellis Amdur had been studying Aikido fo rquite some time. He had a great deal of knowledge, experience, and skill, and was speaking with a friend (who was a very skilled and experienced judoka) about kyusho points. His friend asked about them, and Ellis obliged him with a demonstration. He had his friend apply a choke (hon shime, also known as juji shime) from the front, and then proceeded to press his finger tips and thumbs into the exposed points on his friends side. His friend, unprepared for the shock of pain he recieved, let out a squeak, and loosened his choke, allowing Ellis to get out.
Then Ellis told him to try again, he had something to show. His friend wasn't sure, so Ellis told him to imagine that he (Ellis) was not his friend, but someone who had assaulted the man's wife (Ellis went into a lot more detail, but we don't need to here). His friend went red, and, screaming (Ellis had really worked him up...) grabbed Ellis and began to choke him again. Ellis again went to work with various Kyusho points, but there was not response, no loosening of the grip, and Ellis quickly lost consciousness. When he woke up, his friend looked over and said "Hey, you're up. I'm glad, I was worried for a minute there." "You were worried about me? Thanks, mate" replied Ellis. "Not you. I was worried my Judo didn't work!"
Kyusho require surprise (or compliance), and when someone is amped up (drunk, drugged, high, psychotic, or just old-fashioned adrenaline), kyusho is not something I would bet my life on. But it can be great fun, and is perfect for a number of situations, including security work, and any time you can get the drop on an assailant. Just remember that the street is very different from a dojo, and an attacker in the street won't react the same way a non-adrenalised training partner does. He just won't feel it enough.