While mass murders capture the headlines, you have a significantly greater risk of being targeted by one or more “conventional” criminals. It doesn’t mean that we should ignore the terrorist threat, just that we should keep it in perspective as we train and live our lives.
Likewise, while raging gun battles do occur, they are a rare exception. Almost all self defense shootings involve a very limited number of bullets being fired—as is true for the majority of police officer involved shootings.
It is difficult to determine the percentage of times where the criminal retreated when they became aware that their intended victim was armed without any shots being fired. Anecdotal evidence suggests that this is far more often the case than situations where the defender had to fire their gun. Of course this doesn’t mean that simply having a concealed handgun without the knowledge, skills, and ability to use it will keep you safe.
The take away from all of this is that you should focus your training, especially if it is only occasional, on being proficient at drawing your handgun from concealment and accurately delivering up to about a half dozen rounds as quickly as possible on one or two targets from one to seven yards. Hardcore “tactical” classes can be fun if you have lots of training time available; most people should use their scarce time to concentrate on the skills that they are far more likely to need.