I think context is important here (as elsewhere, lol). If a fight is carried out as a pure exchange of strikes, the way a lot of people (though increasingly less than a few years ago) think of as the basic premise of arts such as karate and TKD, then pressure point attacks are indeed really chancy, at least if you rely on bullseye accuracy in going after very small, elusive places on the body. But in the context of a very different view of such arts—that a lot of their tactical arsenal includes controlling and manipulation, the 'locks, pins and throws' that we're hearing more and more about from a new generation of thinkers in both karate and TKD—the idea is that the defender will be cashing out these controlling moves in various ways, one of which is to force the controlled attacker into body attitudes where valuable pressure point targets can be exploited.
One of the pioneers of this view of pressure point use is the wonderful Rick Clark, he of 75 Down Blocks, which emphasizes the use of controlling techs, latent in familiar kihon movements, to set up strikes at the discretion of the defender. His own book on this, Pressure Point Fighting, integrates the use of pressure points with a view of kata and hyungs which we're increasingly familiar with from his work, Iain Abernethy's, Simon O'Neil's, Stuart Anslow's and a number of others who have tried to recover the holistic application of the karate based arts from the information concealed in their formal patterns. My feeling is that the use of pressure points makes far less sense on the (increasingly discredited) view of these arts as simple punch-kick-block systems than the far more rounded and versatile systems they originally were. So my own best guess to the answer to the OP question is, yes, pressure point tactics can be very useful, if you use the setups for them that are implicit in the kata, but much less so, if you see these arts in a far more limited way as just blocking and counterstriking.
