I play both tank and healer, also got my SAM at 70 so know somewhat the dps role is going to be. As a preference I do prefer normal 1 group pull over multiple, both from tank and healer's point of view considering how little difference it makes in the end (about 2, maybe 3 minuites on super pulling). People usually say that if the tank and healers are capable, the super pull is possible. What people forget is that tank and healer alone does not decide the kill rate, thats where the dps kicks in. So to make the speed run a success every role must fulfill their job.

Problem is that in Pugs there is no telling if everyone is capable or not, only on pre-mades. As a tank, I try to do a single pull on the very first group to see whats our dps is like. I pretty much know what my tank can handle. As a healer I know that I can forget about DPS when the tank does a massive pull, of course it also depends if the tank selfheals or uses their cooldowns properly. As a dps, it depends on which instance. I know my SAM can dish out a good amount of aoe dps, but it comes no where near my single target dps. Which also comes to the next question of, are the DPS hitting the same target. If things die slow, the tank is constantly getting hit by the other mobs that are still alive, has to use more cooldowns which can lead to less or 0 cooldown on the next pack. Just because you DPS/TANK/HEALER think you can handle, does not mean others can. Putting those others who can't fulfill your desire does not mean they are bad. If you want guaranteed speedrun, make a party finder or do it among people you know. Otherwise give indication or suggestion before starting the instance instead of silently pulling more packs. If you can type insults, you can type "lets try more packs see how it goes". Or... well adapt with your current group? If you are forcing others to adapt you, why can't you do the same.

TLDR: Speed runs needs to meet quite a lot of conditions to be successful and even if you can pull it off, the outcome is minimal at best.
OT: There are some people who forces to speed run, yet at some point they stand still doing nothing. Probably sending a chat or something. Well thanks, you have just made our last 2-3 pulls useless.