I agree with the fastrack thing - in fact it's absoloutely obvious unless you are looking at Thorpe through rose tinted glasses. On busy days they may limit fastrack if a ride is on one train, but on quiet days they run one train for numerous reasons; cost cutting is probably the main reason but I'm sure that they use it as a way to sell more fastracks as well - otherwise surely they would react to a 60 minute queue and put another train on?!
In my opinion, the park should start every day on two trains, then if there really is nobody in the park, go down to one. I would be very disappointed if I visited on a quiet day to be confronted 60 minute queues due to the capacity being cut, as well as an hour taken off the park's opening hours (as it usually closes at 5pm midweek), meaning that it would have been better to visit on a Sunday.