The FAA rules are quite clear and apply to the overtaking aircraft, and further an overtaking aircraft cannot use their superior Right of Way provided by 14 CFR 91.113 - 'Right-of-way rules' because the helicopter pilot is the overtaking aircraft and must yield Right of Way to other aircraft already in the airspace. The AMA guidelines and the proposed Part 107 rules will add a rule that an unmanned aircraft will always give-way to a manned aircraft.
For now, if you are operating under a Section 333 exemption, then line 24: "The UA must remain clear and give way to all manned aviation operations and
activities at all times." is the rule. Otherwise the current FAA principal that whichever aircraft is there first has the right of way (except aircraft in distress which always have the right of way).
That's the current rules. But common sense would say, if a helicopter comes into your operating area, move or land. Even if you technically have the Right of Way, the helicopter pilot may not see you, and you have a responsibility to "see and avoid". 91.113(b) says: "vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft".
When you see a gaggle of news helicopters, you can be certain that they are in communication with each other to coordinate their altitudes. It's a small world and they all know each other. If they are in an ATC controlled location, they all get clearance to a block of sky and coordinate and keep each other in sight.