In practice, all the airlines know that most people bash the databases and if a bum is needed on a seat to get something flying, then all that goes out of the window. The requirement for first time passes and high marks is simply a way to wade through a pile of resumes, as any Chief Pilot will tell you. In other words, they are used as an excuse to weed you out.
KayPam - we have had several people take all the exams at once - in fact we recommend it, due to the crossover between the questions. Curiously enough, they mostly seem to be German.