All you want to know
SmartCockpit - Airline training guides, Aviation, Operations, Safety
An anti balance tabs deploys in the same direction as the control surface, making the movement of the control surface more difficult and requires more force applied to the controls by the pilot. This may seem counter-productive, but it is commonly used on aircraft where the controls are too light or the aircraft requires additional stability in that axis of movement. The anti-servo tab serves to artificially increase stability and also make the controls heavier in feel to the pilot (From wiki) Nothing to do with fairing rudder on loss of hydraulics.