There are clearly multiple types of Type 2. Aside from insulin resistance, I think there's also glucose insensitivity. When I was taking orals, I found that, for instance Amaryl, allowed my BG to spike like mad, then came crashing down FAST -- resulting in a massive, debilitating headache for me (and why I had to stop that one...) That seems to me to mean that I had a late insulin response, causing the spike. So my answer is that yes, my insulin helps - but not when I need it. I suppose if I had a meal mixed with slow and fast carbs, the late insulin response may help level off the late ones after the fast-acting injected insulin begins to fade (which is probably why I can manage to eat pizza sometimes without a spike...)
They did a c-peptide test on me, checking for LADA (which they ruled out), but they did it wrong. I really want it repeated both fasting and after intentionally raising BG to provide some real useful information.