When the crew join you in the departure gate everything is wrapped up. Planning was finished long ago, the aircraft started, checks all carried out and rotors running on the hotspot all that is left is to collect the pax.
All of the planning, briefing, and preparing the aircraft is carried out as a crew. You might be under the impression that it is always the captain who briefs you, it is not. Either way the pilot left in the aircraft is more than capable of monitoring the systems whilst the other briefs the pax.
A report time of one hour prior to departure may be the expected minimum, typically you'll find most crews are in before that -nearer an hour and a half- as they are all aware of the variable potential of the schedule; and would prefer to get the planning done and enjoy a cup of tea with the extra time.
This may have all changed since I left, but I don't think it has.