So we did another test, we went to the same Strata Relay, I went in and waited 40 minutes and no players joined, then my Clan Chieftain went in straight after me and it was only 4 minutes before someone joined.
So I re-entered Conclave waited 20 minutes finally got a match where 2 others joined but the second abandoned pretty quickly, and then the player I was playing left early as well, so not even a full round.
Another 10 minutes and another player joined, I manged a kill, and he left...