First of all, you shouldn't consider wearing a down jacket under a mostly non-breathable shell. Down loses most of its insulating properties when damp or wet and, assuming strenuous hiking, having it inside your perspiration saturated outer shell will only degrade its performance over the course of your sortie, to the point of becoming almost useless.
If anything, you need to put the down jacket over your shell. As an alternative, if you really want to put it under and don't own the jacket yet, get a synthetic fill jacket instead. Synthetic fibers retain their insulation much better when wet as they don't collapse like the down plumules do.
Secondly, your description of strenuous hiking is incompatible with a layering system where you're wearing a down jacket permanently. The key to being able to stop for exented periods of time is to stay as dry as possible. Over-insulation will promote excessive perspiration and even though this isn't a problem while moving, the moment you stop and cool off, moisture-logged insulation will make you miserable.
Unless you're doing some really leasurely hiking, operate at extremely high elevation where one step takes 5 seconds to recover, or are doing technical mountaineering with less aerobic performance, a down parka should be carried in your pack until you stop moving.
The main thing is, if you're going at close to 100% effort, you don't need much insulation and you should keep it for when you go 0% effort.
As an example, and I don't pretend to represent the norm, my usual setup doesn't change whether it's 32°F (0°C) or -4°F (-20°C) while moving. I wear a heavy base layer and a heavy WB400 softshell (closer to a true hardshell, it's a winter fabric). My hardshell and down parka are in my pack and only come out if I'm facing extreme wind or taking an extended break. Some days, I won't even use them and they effectively are just part of my emergency kit.