It's technically not a bug. It's just a limitation in how the bars work. Rogues essentially have 3 bars and there are just some technical reasons why we can't go back to the Shadow Dance bar once we've dropped it.
I think the real solution is probably to make it so you can't / don't want to Vanish while dancing. I assume you're Vanishing to get out of roots or dodge spells, but we could solve those in other ways. The spell dodging part of Vanish has been so frustrating to rogues for so long that frankly I'd rather figure out another way to get the same functionality that would feel better all around and leave Vanish as strictly "you want to go back into stealth."
Fivezorz provides glyph and dueling advice as ShS: http://wowriot.gamer...ance-in-General
And, Litreocola provides insight on Gearing/Glyphs/Arena with Sub: http://wowriot.gamer...o-do-Big-Damage
I know this maybe a shameless plug for these writers, but the content in both blogs regarding the current state/patch of Subtlety is top-notch and will be well-worth to read. This isn't an effort to make a profit off arenajunkies community(All the writers pretty much make slave wages), but to make sure that the effort Fivezorz and Litre put in to make these articles goes noticed.
Serennia and Jasi had it good, they both made about 10x more than any writer(including myself). On that note, for those who hate WoM and what it is... At this point, it's pretty much community service. I make more in 1 day at my day job at an accounting firm than I do from writing blogs(for a whole month) that take 4-12 hours to write(the best-in-class blogs each have taken 12-16 hours each).
I want to list the millions of problems wrong with Gameriot, but they would delete my post immediately... The website was seriously only 80% finished by the original coder, he basically worked on making it look pretty instead of making everything on the backend function properly and peace'd out when he got paid.