Farsight counts as a Monstrous Creature in hand-to-hand combat, so he ignores Armour Saves and rolls 2D6+S for Armour Penetration against vehicles.
Any Tau unit in an army led by Farsight may improve both their WS and I by 1 at the cost of +5 points per model.
5
3(5)
3(4)
4
10
3+