Cari, I hear you.
I'm 5'9", 16x lbs, and a solid size 12. I have a good friend who's about 6'2" and a cyclist and she's the biggest I know (but she's skinny). No other cyclist I know comes close to us in height (but I've seen some bigger - i.e., heavier - riders). I have a long standing argument with my LBS about women's clothes. He likes to carry high-end stuff like Descente and Castelli. Nice stuff, but size L in Descente is snug on my and I need XL in Castelli (yet I can wear size M in Cannondale...go figure...but it's short). He NEVER has that size in stock and he wonders why I rarely buy clothes from him! Bike clothes seem to be all over the map.
TE will probably banish me from their list, but while I love to shop TE, I've never actually bought. Unless I know the brand well (Shebeest is okay, but runs short, Pearl Izumi is wishy-washy....somethings I can do M, some I need L), I generally don't do mail order. I must try it on first. That's why I'm hesitant to try those CW-X tights I mentioned in another thread from Sierra Trading Post.
p.s. I can't believe the woman from Shebeest was "offended." She should take some constructive criticism from possible customers as an opportunity!