Occasionally, when all else fails, you need to dispense with a waypoint. Fake one with a gamelogic and move command.
However, I would say that putting a group into S&D is not one of these rare occasions. S&D is excellent for having loons milling about: if it matters at all to the mission where they go then don't use it, use a sequence of move waypoints instead - it gives you much better control.
What kind of unit are we talking about here? Increasing skill might help in reducing the delay.