A thought that comes to mind is this.

The truism that a chain is only as strong as it's weakest link can be applied here in terms of speed. A dungeon can only be run as fast as the slowest player in the group. If a tank happens not to like large pulls, or is not comfortable with them, no amount of DD running up and face-pulling mobs will help the run time. If anything all that does is slow things down even further since the Tank now has to regain hate, re-position everything and then settle back into the normal tank role.

It's quicker to optimize the run with the players you have than try to force them to conform to your demands.