but how come its usually the handling pilot/aircraft Captain that gets a DFC whereas everyone else in the crew often receives 'lesser' awards?
It's usually a function of the command and decision making - everyone else on board gets to support the decision maker and the outcome lies firmly on his or her shoulders. The individual actions of the crew are effectively combined to drive a successful outcome based on sound decision making by the Captain. Everyone on board makes significant and selfless contributions, but only one person holds the full responsibility and accountability for those actions.