Destiny is a social game - or it is supposed to be, at least. However, if a friend is doing a particular activity, it can be very difficult to find out who is in it to join them. Going through each individual friend on your list is extremely time consuming and it could be easier, especially since the game is already aware of how many people are in the activity, as shown by the fact that it says x friends are doing it. My suggestion would be to give a list of emblems on the Launch screen. That would make it far easier to join friends in active activities. This could be limited to those that can actually be joined (i.e. space on their fireteam and you are capable of joining them - i.e. set to open or friends) and only showing one fireteam member from any fireteam if there are a lot of friends in it.