I encountered this bug today. I did it w/a friend. I am a Sylvari guardian. We killed all the pirates (not easy!) and then Tybalt said he’d meet me back at Lion’s Arch. The mission log up at the top right still said I needed to kill all the pirates. I assumed like a previous poster, that the turrets needed to go. Got rid of the turrets, it still said I had to kill all the pirates. Looked everywhere, found the NPC pirates but they could not be killed. Went back to the green star area, but there was no waypoint to get out and go back to Lion’s Arch. Looked at this thread and the person above me suggested just running out of the instance…well I did that…which caused my entire mission to reset. I am demoralized at this point.