The main cause of "One Shots" is lack of game knowledge.

Try to do it with 17 minions on the map, and if you play ranged minions, put 2-3 flamewalls on it and you'll see a big nothing on the map. So these mechanics don't work the same for every class, that's why I gave up ranged minions so that at least the flamewall wouldn't cover half of the map, it's a bit better but still weak...