Duty Finding Syrcus Tower for tanks

Hello just thought to post here to see if anyone else is having difficulties or really long wait time to build a party or join a ST in general. I've signed my PLD up to get into this duty and for some reason it pairs me up with no one. Today I try again waited for 10 mins switched to DRG then I'm paired up with parties before the duty starts with 2/3 of tanks being there. Why wouldn't it just place me into the group that needed the last tank? It doesn't and it bothers me cause PLD is my main. So any thoughts on this would be appreciated.