The mystical dragon has finally been released to non Chinese servers. It requires you to sign up for 2-step authentication for your GW2 account. You have to use a mobile smartphone for this process Dulfy has provided the following link for a walkthrough: http://dulfy.net/2015/07/28/gw2-exclusive-mini-mystical-dragon-for-using-2-step-verification/
Update:
In a few weeks, you can choose to use SMS phone-based security instead of an authenticator application. You will receive the mini by using the SMS route. Anet Security Article 7/28
Video of Mystical Dragon