He's been worse than I thought - I expected him to burn his bridges in season 3 and not this bad. Still, I'd take him over Moyes any day of the week. Moyes was comedy for me, the way he tried to con the fans and lower expectations and mentality to his comfort zone.
Moyes thinks like a loser. For all his flaws, Van Gaal thinks and acts like someone who belongs at a top club. For that alone, he will leave the club in far better shape than moyes could have.
I don't think he is as bad as he is delivering. I think he could even turn it around for you. Problem is, he's not turning out to be the great bridge between moyes and the next guy people thought as there are few managers out there who would build on what he's made. Guardiola and maybe Ancelotti but.... Pochettino maybe?
Mourinho is going to want to tear it up and start again if he comes. Has little to work with to suit him in this side.