While High Elves are a very cohesive faction, it is this unit that drives their strategy more than any other. Law of Fortitude is very powerful and because it’s a ranged unit it’s easier to help only your own units and still be an active participant in combat. If only your units are affected by the aura, no unit can match the amount of value this unit brings to its faction. To give some perspective, without affecting the opponent it’s a 2/4 ranged unit that gives +1 life to all friendly units in its range every turn!
This unit is the reason that the High Elves ranged game is very strong. Your opponent is kind of forced to position their units in a way that is not easy for the High Elves player to have a unilateral advantage of the law. 
Try to have at least one of these units out and don’t be afraid to have several of them out. The law they bring is the core to this faction’s strength.