I refuse to train novices using lasers or dots. I want them to learn to use iron sights first. Dots are not a crutch, they are an enhancer when used properly.
Having attended LEO RDS for duty pistols instructor courses with fellow LEO instructors, the general consensus was that the presentation of the gun is key to finding the dot quickly. But then that is true with irons as well. I am now convinced that training with optic mounted pistols improves your iron sight performance due to improved presentation of the pistol technique.
I have put many thousands of rounds through several pistols with optics. It is an acquired skill. I am still experimenting with which size, shape, and brightness of dot is best for me but am coming down to a smaller dot. I think it is essential to have iron sights visible and co witnessed with the dot in the event the optic fails. Dots require training and practice,just like irons. Many are frustrated with the dot because they have not mastered the presentation or focal point. Keep working at it and it will fall into place.
I am of the old school in defensive shooting, which is get multiple solid hits center mass in a hurry and forget about hitting the "X". That was a big paradigm shift for this old war horse brought up on revolvers shooting for the X on the PPC. Save the "X" for competition. I remind folks of the Rule of 3's. Most lethal encounters are at 3 yards or less, 3 shots are fired, and it is over in 3 seconds or less.
I have discovered that I am capable of greater precision with iron sights, but much faster getting multiple hits center mass when using the dot. Precision shooting is still important and I practice hostage rescue drills every week to keep that part sharp. And now and again take it out to 100 yards.
Ultimately, a balance of speed, power, and accuracy wins the day and use whatever gives you an edge.