IMO an experienced tank only run very fast when he thinks the group is good enough and capable to do that.
I will be glad and appreciate when I was a healer or DPS and having such a great tank who make the content really fun.

Ofcoz I don't feel the tank is bad if he pulls one by one as long as he has concentrated on the fight.
But in practical, I found some ppl running dungeons while chatting with FC (keep mt to the Party about discussing BiS with FC ..etc ^^; )
or preparing food (suddenly brb before boss bcoz the pizza is done after 3min oven... when did the oven start? when pulling the 3rd pack? ^^; )
In above cases I think that player may perform a lot poor due to human multi-tasking limitation.