ive always referred to qsing as a cod specific term. but generally applied its essentially just having a fast sniping by aligning the shot before you scope in. giving you ideally, the fastest scope time possible between scope to shot.
now as far as quickscoping related to cod, theres an eternal debate on whether or not its something thats cheap, exploitive, vs a skill difficult to master. Ill say that in that context id agree that both its easy to learn (if actually doing a proper "quickscope"), but difficult to master consistently.
In max payne 3, quickscoping doesnt seem nearly as important. In this case its really the opposite for the majority oif players, auto aim for all the other guns, but sniping is completely free aim, giving you more precision, but less cpu assist. This could be seen as a strong disadvantage for those unfomfortable with the free aim. I guess, in a way, quickscoping still works well for the mid to short range encounters (just as cod) if you can get use to the aim reticle orientation, and learn how to be as quick and accurate with ur shots after the initial zoom.
but in the end wouldnt consider it the same as traditional cod shit. no heavy aim assist with snipers, no sway or zoom, not realy ADS time.... qsing to me, more or less its just a phrase for "sniping fast" in max payne 3, which is a valuable tool for anyone.