A static is the best way to clear content in my opinion. It's a good way to learn play styles and to get an expectation of how people play in order to overcome the raid. That's not to say that pugs aren't good because they can be, but pugging is an adjustment for every member of the group that has to be replaced and adjusting to that change is a challenge. That is why I believe that some PF groups don't survive the initial few runs.