I would not personally use "Expedite Descent", I could only forsee 3 scenarios when it comes to level clearances.
1)'When Ready .....' with a possible requirement to be level somewhere...
2)'Descend XXX with XXXXFPM* minimum (*Insert XXXMPM when Metric)
3)'Traffic 12 o'clock 6 miles descend immediately* (*with additional - Like your life depends on it...because it does)
I see no need to say expedite descent as it far from being a POSITIVE control action and does NOT ENSURE SEPARATION.
Of course that would not preclude the use of Expedite Descent for controller amusement.
I await to be corrected by my learned freinds.
