Having a tank pull a whole floor of mobs doesnt make a run faster, it just makes it more tedious for the healers/ dps.
Many times you'd actually save time by waiting just a second or two.
You say you dont care about anyone else's deeps, but wait a second, say you just pulled a tyrannical boss, and i'm in multi/aoe gear, unstealthed and i couldnt even prepot ! Oo
So what gives ? boss dies slower than usual. Maybe you'll even wipe just because you couldnt wait for a second.
Now you're officially an ass for the whole group.