I always wondered why you cannot broadcast what you are trying to do. Like for example, why can't a beacon hover above my guardian's head while I'm at the tower? To keep it simple, how about make the player's name slowly flash or have an icon next to their name? That way, they can broadcast that they are trying to do an activity and would like to form a fireteam. If you select that player and then see details about them, you would see what specific activity they are trying to do and then you would be more inclined to interact with them.
I know there are players out there who go solo nearly all the time and they hit roadblocks in the game because the game's communication platform is not inviting.