You are correct that a hardshell, softshell, and baselayer cover most of your upper body clothing options. What you need to add to that for cold temp. activities (~ <30 degrees F) is a down or synthetic puffy jacket. As someone observed above, the soft shell is meant to keep you comfortable in variable conditions down to ~-20 degrees, but only while highly active (backcountry skiing, climbing, running, etc.). As soon as you stop, for a snack or whatever, you pull on the puffy for warmth until you're ready to move again. I have a couple of different weight baselayers that I wear under the softshell dependent on anticipated temp. and what type of activity I'm doing. If your body "runs a little colder" then mine (I seem to be an oven), you may find that a fleece vest or even a full lightweight fleece under the softshell keeps you comfortable while active in colder temperatures. For longer trips, I often throw an extra midweight baselayer in my pack in case temps drop or I find myself feeling too cold.
Bottom line: your layering combination (baselayer, fleece if needed, softshell) should keep you warm without any sweating during prolonged aerobic activity, your puffy jacket should be like a half sleeping bag with arms for when you're sitting on your bum.
Final ramble: I play in CO and MN, both very cold, dry climates. I have never felt the need for a hardshell in the winter months here. If I move to a coastal climate, I'm sure I'll make some adjustments. Most likely I'll add an ultralight hardshell to the Oh-Shit-Kit for the ugly storms. I can't really wear them anytime else because I simply sweat too much.