Not enough rudder authority during takeoff roll
The rudder authority is correct. The Vulcan used nosewheel steering until the rudder becomes effective around the 90kt (from memory) mark which is why you will see the elevons down (stick forward) if you watch take-off videos of the aircraft. Unfortunately, FS has a rubbish ground friction model and you tend to lose NWS too early.
Line up properly, respect crosswind limits, lead with either left or right throttles and occasional left or right brake are about the only advice I can give on that, sorry.