There are several significant drawbacks to the new implementation, which adversely impact the utility and usability of TradeSkill hyperlinks. Most notably, TradeSkill hyperlinks can only be opened if the character GUID embedded in the link has already been encountered by the client during the current login session. This has a number of significant negative implications:
1. You can only open TradeSkill hyperlinks from characters that you are grouped with, chatting with or standing near in the game world. Any attempt to open links obtained via other means will silently fail.
2. For example, this means that if player A whispers his TradeSkill link to player B, and player B whispers it to player C, then player C will be unable to open that link unless he has also directly "encountered" player A during the current session.
3. In particular and more annoyingly, you can no longer open tradeskill links for your ALTS (eg saved by an addon or even "whispered back" to you from another player), because the characters on one account never directly "encounter" each other in the game world. Nor can you whisper a working link for your alt's tradeskill to another player, unless that other player has already encountered your alt during his current login session.
4. It's no longer possible for addons to forge an "all recipes" TradeSkill hyperlink that can be clicked to open a tradeskill window containing every available recipe
5. It is now possible to forge links that "spy" on the TradeSkill recipes of any character you encounter in the game world. It was already possible to see any character's trade recipes via battle.net, but now it can be easily done with a macro directly in-game.
These are all regressions in behavior relative to 5.3, and represent a significant degradation in the usability and utility of TradeSkill hyperlinks. It has a side effect of breaking certain addons (notably ProfessionsVault), but more importantly TradeSkill hyperlinks are now far less useful than they used to be, even with no addons at all. Please consider rolling back this terrible change, or fixing the implementation to address some of the drawbacks listed above.
There's an addon developer discussion on this issue with full details here:
This thread was started on the PTR Bug Forum, the old thread is here:
EDIT: Blizzard has finally acknowledged the problem (later in this thread). Still no ETA on a fix.