2 seconds is too long:
Moving introduces a whole additional set of variables. Is the way clear? How many feet of unobstructed movement do you have? Have you practiced it enough that you don't need to think about it? If you move, will you trip? Run into some heretofore unseen object? Again, proponents of moving ignore some very important and real issues: it is not without risk, it adversely effects hit probability (which is the most important factor), no proof that it has any correlation to survivability (just like there is no proof that not moving is more likely to get you killed). Many continued to hold the belief that the world was flat for a long time after Columbus' journey. Doesn't change the facts.
Anything that requires thought is detrimental in the time aspect. Whatever your response is, it should be second nature. You don't want to try to formulate a plan while locked in mortal combat. You need to know ahead of time what your response will be.
Much of what has become the "new doctrine" is based on fallacious interpretation or downright desire to create a need for the trainers to fill.
The "Tueller Drill" is a perfect example. Many trainers cite it as proof of many different things. In fact many have never read Tueller's article. If they had, they would understand that the main point Tueller was trying to make was that officers should have their weapon in their hand at the first sign of trouble. Not that a knife is a lethal threat at 21 feet, nor that you need to hit the target twice at that distance in 1.5 seconds. The same applies to civilians, have your weapon in your hand at the first inkling of trouble.