You do realize that Halo Wars is an RTS game, right?
In an RTS, every unit has to have its own unique role on the battlefield. Hunters were chosen as the infantry that can destroy vehicles (and rightfully so). Of course it doesn't have to make complete sense, nothing in RTS games really does.
It doesn't make sense that Locust inflict severe damage on military buildings but inflict minor damage to every other type of armor... but then again, a locust that can destroy buildings and burn away enemy units from a mile away isn't exactly fair, is it?
You may realize that some aspects of the game are not practical... but you'll just have to accept it. Talking about it would just be talking about the obvious.
Code of Conduct. Obey it!