I expect that most of us can point at and hit a man-sized target without sights. The question as I see is; can you do that without raising the pistol to a normal sight line, say from the hip or across your body or some other unconventional pose. Not all fights occur standing. That's when a laser helps.
I don't see this as practical, sorry. The listed applications:
From the hip- you mean, like a Western gunslinger on a quickdraw? I have to say, if I were ever to feel so endangered that I was compelled to shoot ala Josey Wales at someone instead of waiting until I had the gun in proper position, I darn sure won't be waiting until I acquire the laser, I'd have a couple-three rds fired by that time and the gun would still be coming up to a better position as it occurred. And I would be moving too. So the laser would be irrelevant at that moment.
Also- I have a family. I'm not inclined to do a rapid quickdraw shoot when something startles me in my house, as I might kill my son while he enters my room or goes to the bathroom.
Cross-body; you mean like in a car? Not waiting on a laser, again. If I'm that threatened as to fire while in the car, the target is close enough to hit without using any sight picture. If it's not, I'm getting the car out of there, or taking a more covered position. I'm not shooting like a gangster in a driveby. I've got to admit, I'm probably not prepared for some type of Colombian style ambush/assassination attempt (block in the car and riddle it with bullets), but if it happened to me, I doubt a handgun would be of much help then anyway, laser or not.
Not all fights occur standing; ok, the only way I see being seated as a hindrance to getting the gun drawn to a good position would be tight at a table, say at dinner. If I can't get the gun over the table, the laser is probably painting the table from underneath, or the table is obscuring the part of the target that is being painted. Either case, I don't see the laser.
Also, please keep in mind the realistic truth here- the amount of time it takes to pick up on a bouncing, shaking laser dot, while you are primarily focused on the threat at hand, is probably longer than it would take to physically raise the gun to a more natural and effective position. It's not very hard to point (using your hand and finger) at something rapidly, while you and the target are both moving. It's a lot harder (at least for me) to scan for and confirm a quivering dot that I'm attempting to direct and control, while I'm under extreme duress and taken by surprise. If we're both moving, I'm not saying I am landing direct hits every shot, but I'm definitely going to get a couple shots off quicker and more on target by pointing, than by trying to track a bouncing dot. Pointing- thrusting your arm out between yourself and the danger- is a reflexive move, and having a gun at the end of your arm is a conditioned adaptation of that reflex. Picking up a small dot isn't reflexive, your natural reaction to any visual distraction is to be still and look at that, to bring it into focus. That could be disastrous in such a scenario.
Now, gun presented and you're sweeping, using a laser instead of relying on proper position as indication you're on target- ok, I can understand that. I just don't do that myself, I'm a lot more comfortable knowing (feeling) that I have the gun in the correct position to shoot accurately enough. It would seem like the laser would be one more thing to have to process, when your vision and mind isn't in a multi-tasking mode.
And again, I don't mean any of this in a hostile manner, and I suppose you could always list isolated circumstances where a laser would help with defense or training. I just don't suscribe to the device, myself. To each their own.