That's not necessarily true...running QB's that are accurate, can help any team.
Watch Mitch Trubisky this weekend...or highlights closely....Throwing on the move is a very successful scheme...Guy outta Denver...Shanahan used it with much success. With play action passing...the roll out pass is an excellent way to get the ball downfield...deeply.
I agree, qb's that are accurate, who have the ability to run are very tough to stop. I don't qualify pass first, accurate passers as running qb's just because they have great running skills. Running QB's are Mike Vick and Tyrod Taylor, maybe even Aaron Rodgers (the more I watch of him). They are guys that rely on their running skills to have success. If you take away their pocket movement and force them to throw, their success drops significantly. Those types of guys can make bad teams mediocre and good teams mediocre and don't have long term success. They are too reliant on the play calling and their running ability to be a truly elite QB. So I think the problem we have is that we don't have the same definition of who a running QB is. QB's that can run certainly add an advantage but only if they are good QB's too.