Hmm.. I mean, I hear what you're saying, but I feel like the shortcomings are being addressed by my rain layer.
You say it'll be part of a core-warmth management layer for highly aerobic activities, which is exactly what I'm using it for. While static, you say the sleeves and the hood provide warmth, which is exactly what my rain shell provides me. I'm not bare-skinning up the mountain, remember; I've got at least a baselayer, more in sub-freezing conditions.
As far as weight penalty goes, if I was trying to go as low weight as humanly possible and nothing else I could probably slip under 1 ounce. What kind of durability am I looking at? Slim to none. Durability matters to me, so don't quote my 3.3 oz brag as a claim at finding the lightest. I found the lightest at a certain standard for durability.
Besides, the weight penalty is not a fair comparison. The Houdini might be only .7oz for sleeves and a hood, but as another forum member stated before, as you increase weight you can mildly correlate an increase in fabric quality. I checked in to the Dead Bird camp specifically so I'd get something durable, since I don't want pinhole tears in my windshirt after a few weeks of use. If you compare it to the Incendo Jacket, I'm cutting a full ounce, plus the associated, let's say, 20% reduction in bulk. Seemingly irrelevant, but when you're packing everything you own for a month into a hip pack, a frame bag, and a stuff sack, an extra 2 inches of compressed material can be a make or break for even bringing it.
Let me emphasize that; if the benefits of the item aren't above the bulk penalty, it doesn't come with me. If it rips at a sneeze, it doesn't come with me. I biked across the northeastern U.S. without a windshirt, and I used my rain shell on peaks. The phrase "Skimp on ounces elsewhere" implies that this item is a necessity, which it is not.
I think the decision to get the vest as a core piece during aerobic activities was a good one. Maybe I'll get a full hoodie down the road, but I was a skeptic from the beginning of this thread because I had simply never felt the need for a windshirt. It seemed to me to be another UL item touted to backpackers to get them to spend more money. I am now a believer that there is some value to be had, but I see that value to be a way to keep your comfort up while you're plowing up the mountain, which is the one area I can say I'm almost always too warm or too cold in.
For this aerobic activity, the vest balances the durability and weight I'm looking for to dip my feet.