We've tested this skill internally, and can confirm that it DOES have a 100% chance to stun. One important point though is that the trade-off for the guaranteed stun chance is a sharp reduction in the stun time; with a level 1 glyph, the stu…
This has been fixed in the Chinese version and will be implemented in our next content update. To head off any speculation, though, I do not currently have any information on when that will be released.
Unfortunately, technical issues are going to prevent us from performing maintenance tonight. We are rescheduling for tomorrow at the same time. We apologize profusely for the delay, and thank you for your patience.