I think Demigods should have collision with themselves.
I'm not.. 100% sure with demigods colliding with troops.
I think, idealy, the demigods should "wade" through troops. Like, their movement is slowed to half or 33%, they attack units in their way doing damage(in the Rooks case, stepping on things and instantly killing like supcom experiementals. But, like i said, much slower movement speed. It'd be less effective than normally attacking.).
And as you "wade" through, some units should jump out of your way and such, a mechanic so that the wading through wouldn't be more effective at killing things than your normal attacks.