Can’t pass “Storm the Castle” mission

I tried like 4 or 5 times to do the “defeat warlord” part and the hard thing isn’t the mission itself, I either arrive at the legacy fortress too late and some sweaty squad cleared it before me or a squad clears it AS I’m doing it. I could easily do it if other players won’t stick their noses in it. Is there a way to do it solo? Or any squad willing to help?