I've found that Torchwood does what it was intended to do quite well: show what happens when humans try to do the Doctor's job when he isn't avaliable.
Namely, they can't cope so they get emotionally and mentally creamed.
The 456 could probably have been defeated in an in-show twenty minutes if they had managed to contact the Doctor via Martha (who was on her honeymoon and thus unavaliable apparently).
But if they had... there wouldn't have been any drama would there?