the reason this is useful is mainly because of the base order ID. This is because usually when you use a dummy spell derived from the base spell, it will cast every spell at once, so if you just change the base order ID, this problem is solved. Also you can change the target type - instant, like roar, taunt, etc - unit target, like frost nova, holy light, etc - point target, like crushing wave and others - both point and unit target, like shockwave, carrion swarm, etc. It also has the AOE choice too which is helpful. So channel is pretty much a fully customizable dummy spell and can be very useful when you cant find the right spell for a dummy.