Running and gunning actually does work (provided the lead person is doing a good job clearing and keeping it moving).

An example of this is where we were in the hospital map. One of us got barfed on right when we exited so the hordes came and everyone sat in the saferoom...except this one dude. He broke off running through these hordes and a few seconds later had already called the elevator. By the time the 3 man team made their way up to the elevator, he was there waiting with the entire rush already over. And the infected that tried to get him were dead. The team then got everyone to the safe room a minute later as he mowed a path down. It was pretty crazy, and it was on advanced.

I do think though, a slower team might make it work. The problem is the director. The director seems to spawn tanks (on any difficulty beyond normal) quickly. This makes it almost impossible for any team to get anywhere provided there is some coordination between the infected to corner the humans with the tank. It also seems to spawn it not according to which team is behind, it just does it for both teams.

I do want to say though, like Sirusblk pointed out, a good team is the only way to beat a finale regardless of the running and whatever. I still think finale should be calculated differently or have a bigger difficulty modifier than 2x since its rare for any team to beat it.