Okay, I'm going to bring up a point here that seems to be mostly ignored: the meaning of 'chain pulling' can be different between people.
Chain pulling does not have a set in stone definition that means... well, any specific thing. Meaning that it is not required to literally 'never' leave combat in an instance in order to chain pull. The tank does not have to pull the next group of mobs while the remnants of the first are still attacking him in order to chain pull.
Honestly, as melee dps it annoys the living daylights out of me when tanks run that way. Still, I don't bother saying anything about it to them because it's, presumably, just the way they like to tank. Heck, I even have a guildie tank who does it all the time, but I'm not going to give her flak for it. Sure it's a bit annoying, but to each their own.
Having said that though, no, that's not the way I pull on my tank, but yes, I do chain pull by moving continuously from one group to the next as each is downed, meaning everything dies before my feet move. The only exception to this is in situations similar to the paths before the first boss in HoL, where individual Iron Dwarves aren't linked to anything else. So sure, I'll snag them and bring them into the next group, where the fight will actually start.
Maybe a little off the original topic of the threat, but it's a simple point. Not everyone works the same way, nor do they have to.