Why Speed Pulls?

[Moqi]

But just how much time are we saving here?

So little you can barely notice. Hell, I had a tank pull every single group separately in Braflox HM, and I never felt it was taking that much longer than room-wide pulls.
At the end of the day I play to have fun. If those 40 minutes I spent in a dungeon were enjoyable, who cares if I could have done it in 10, game served its purpose anyway.