In a hurry, you only have one hand on the gun and you point the front of the gun at the fellow who is going to fire at you in .05 seconds. The only thing you have time for, is the front of your gun (front sight) and then fire.
Anything that slows you down from that instant firing, is a death trap. If the dot sight requires extra time to focus on that front sight, then you lose if that is the time frame, simple math, simple physics.
On a non carry gun, who cares. It if helps, go for it. Guns for fun are different than guns for survival, they are never exactly the same. That said, nobody reading this is likely to ever have that actual event, so just buy what you want, put it on your guns and enjoy them.