I think 1/3 full might be too low if you're looking for big taste. How big is your gaiwan? I've used as much as 12g in my 150ml one and as much as 10g in my 100ml one (similar to DanCong). I get the best results when the leaves lie just below the water level. I think the leaf surface area to water ratio is much more important than the leaf's mass to water volume ratio. Also, my first infusion is a rinse followed by a 10 second infusion, then 20, 40, 60 etc.
I've found that many things labelled Da Hong Pao tend to smell amazing but the smell doesn't translate to taste! Perhaps I am brewing incorrectly as well or my water quality is wrong.
Okay, this gives me something to work with, thank you. I will try adding more leaves to the gaiwan. I mainly use my 150 mL for DHP, though I have a couple of 120 mL, as well.
I think that part of my letdown was that I expected a big taste like the one I get from the Rou Guis I really enjoy, which have quite a different flavor profile. And I agree with your impression that the smell of the leaves (wet and dry) does not often translate into taste.
Also, thanks for mentioning the aged Rou Gui. That sounds like something I'd really enjoy. Also, if you haven't tried the Mi Lan Dan Cong AAA, I highly recommend it. It's one of the best oolongs I've tried, and it holds up to many steeps.