When it comes to targeting for self-protection, you have to keep things very simple. The skill to impact a specific weak area on the opponent is of course a high-reward component of your striking strategy, but those locations, and indeed the probability of meeting your desired accuracy needs to be kept within the realms of reality. An exploration of vital points, TCM, small surface striking and similar fine motor control studies is no less a valuable part of a martial artists journey and enjoy these studies too, however, with Murphy's Law being ever prevalent in the application of karate for self-protection, we need to keep the notion of targeting as fail-safe as is possible.
In the quest for simplicity in my core application methods for self-protection, I discarded individual target placement years ago, instead switching to identifying and employing the use of large target-rich zones on the human body. Optimising even further, I started to align my striking strategies according to the three levels often given in traditional karate...these being of Jodan (upper-level), Chudan (mid-level) and Gedan (low level), defining them as follows and being applicable 360 degrees around the body...
Jodan / Upper-Level...
This is anywhere from the collar bone to the top of the head.
Chudan / Mid-Level...
This is anywhere between the collar bone and hips.
Gedan / Low-Level...
This is anywhere from the hips down to the feet.
In terms of priority for self-protection (which is scenario dependant of course), Jodan is most important, followed by the Gedan and then finally Chudan. The reason for this order is that striking to the high-line generally offers more chance of affecting the enemy's consciousness and/or willingness to continue, therefore allowing more probability for subsequent escape. The low-line provides greater likelihood to disrupt mobility and consequently, the ability for the enemy to give chase. The mid-line comes up last simply because it is more likely that the torso will be protected to a greater or lesser degree by seasonal clothing. So unless you are protecting yourself against a motorcyclist whose wearing a helmet and full protective gear, the high-line and low-line are generally more available, less protected and provide the best opportunity in terms of target selection for maximum effect.
Aligning to large and rich target zones rather than smaller vital points or weak areas makes things more simple and effective to apply under stress and offers a far greater level of redundancy. This, coupled with the delivery of successive high impact blows and a strong attitude to prevail will provide the best chance of overcoming the threat and thus, maximising safety.
It also allow you to make quick decisions and change tactics more swiftly without being bogged down in the detail. For instance, it is difficult for an opponent to successfully protect both the high and low level together, so if one strike path is obstructed then you can easily switch to the other. This facilitates the ability to press forward and employ a continuous barrage of strikes - a concept readily expressed within karate's classical forms.
Even with years of experience, effective targeting can be one of the most difficult skills to achieve during the mess of a live altercation. So it makes sense that we find ways in which to reduce the consequences of failure due to this component. Thus, equating to large target-rich zones, developing powerful strikes, honing simple tactics to negotiate barriers and fostering a strong asymmetrical attitude will help to significantly increase the chances of success.