I still think the marrowkai have the advantage here, unless of course your not very good with using marrowkai. Then your in trouble.
The point of this is to show skill in using those units... Micro.
And if both players had lots of skill, I don't see why marrowkai would lose (they could build them faster, so they would have more marrowkai than order has magikill). Longer range for reaper, reaping every single magikill, hell fist with every single one on ALL magikill, and then retreat when you need to reload reaper.