Aww, my heart fell when I read that about the Chinese green tea. My advice - get it fresh! the 2012s were excellent, and I went through Tea Spring, Norbu, and Yunnan Sourcing US for mine. I recommend another go with fresh greens next time.
Your observations are normal. As your tastes develop, and you become more in tune, you'll find a bell curve. Most tea is middle of the road, some is stellar, and some is just shit.
I wouldn't necessarily base opinion on what was experienced just with one vendor. Get samples from lots of vendors - that way you have a broad spectrum. Maybe even get the same tea from different vendors (especially helpful with pu-erh, as different distributors store their tea differently - which affects flavor).
Good luck with your search, and welcome to the forum!
Peace, love, 'n tea -