The 100 Wiki talk:Episode Update Checklist/@comment-26152791-20160407010318

3x04 and 3x06 done for Monroe. She does not appear in any other episodes so far.

3x04, 3x05, 3x06, 3x08 done for Miller. He does not appear in 3x07.

3x04 and 3x08 are done for Harper. She does not appear in  3x05,  3x06 and  3x07.