what fights are 3 minute on progression? I think some of the fastest kills in the world on Iron Jugg now with full BiS raids (or close to it) is down to around 3min, maybe some of the first 2-3 as well. But on longer fight the "trick" is going to make less and less impact (% increase), I'm not saying it isn't a increase in damage. I'm saying IF you chose to do it then be aware that combat locks your gear in place which makes you look bad, ninja pulls can be salvaged even if people lose pots. Having one (or multiple) raiders stuck in "special" gear is not salvageable in a progression state, imagine if you were set to do the engineer on HC Garrosh and you got locked in wrong gear. Now you have to be that guy that says on vent/mumble/teamspeak that you have to wipe or have a backup doing it, even if it's one out of 100 pulls that happens to you that's a wipe credited to you and as far as I'm concerned that's as bad as dropping a desecrated weapon in the wrong spot or running away with malice or kiting Thok through the middle of the raid.
What I'm trying to say is this, do you want to risk a 2m damage done increase with a instant wipe during progression?