Actually, when limited to 5 man Crews, (Obviously larger crews afford more intense coverage) the above diagram describes effective coverage.
The BJ, with support from the U provide "front line coverage (False starts, lineup issues) short (onside) attempts, & the ability to move along the sidelines to observe play both prior to & after a kick is made and during any subsequent advance on either (both) sides of the field, including support to the Referee of any action should the ball penetrate the Goal line & subsequent action move towards either side line. The R is in position to observe the ball penetrating, or be carried into the EZ, and to follow any subsequent action towards either side line, with assistance from the L & LJ.
Should a "runback" occur, back into/up the field of play, the L,BJ and LJ,U will escort the action (continuing their spacing, observing action, with the R observing action from a following perspective.
Certainly, additional "eyes" would be helpful, but a "5 man Crew", where circumstances limit the coverage to 5, has proven effective when competently executed.