I think it would be useful to be able to place context sensitive markers on the ground or on a entity.  It would work by holding down a key and clicking on the place or thing you wanted to mark.  the other demigods would get a brief message and be able to see the marker on the field and minimap.  If the marker is not in the visible area, an arrow would point in the direction of the marker.  The contexts would be things like, "attack this [object]", "defend this [object]", "heal me", "defend this area", "capture this flag".  the marker would last until you placed a new one or the target was destroyed.  I believe this would improve team cohesion and tactical effectiveness.