No group finder?

I've got the game and am in a small 'guild'. So far I am reliant on friends or guild mates for grouping, but they are small in numbers and no online all the time that I am.

so how do I team up with people for strikes as there never seems to be anyone automatically join in with me when I set my strike to 'open to the public'? I need to find more people to play with but I can't seem to see a simple option as there isn't an open world to engage with people. Any thought?