There are several occasions, particularly tankering sectors, where I will not finalise fuel until I've had a chance to see what is happening to the ZFW; remember quite often the planned tankering figure is MLW limited. Bitten badly once by this, and had to offload pax with hand-baggage only onto the next flight (no inconvenience to them, we were already delayed by a late inbound and they only arrived about 10 minutes after us.) In those instances fuel required can and often does go down instead of up.
Also with regard to the CIRRUS tankering figure it is in my experience almost always wrong; carrying the exact figure will lead to the next sector having up to 400kg LESS then the CIRRUS planned return figure, mostly due to inaccuracies in the taxi allowance ex-LHR and a burn figure that at my most charitable I will describe as optimistic.
I'm never one to knee-jerk against change, but am seriously struggling to see any benefit to this new system. With an operation of the size and complexity of BA's shorthaul Heathrow set-up having a person at the front end of the departure who could juggle the figures around at the last minute was a godsend.