1 person has injector, enters instance and /ejects trades injector to next person, they do teh same, etc etc, from that point on all these people can enter sher kar as you dont need the key other than the 1st time.
happy to test this out - zakx has a key, and I'm keen to get a bit of loot from Sher Kar..... Also have the 'hard' bit towards making another key, so when next on Musty, will try to get a 2nd key made