http://www.wowwiki.com/Flurry_(warrior_ability)

all normal attacks will consume a Flurry charge
Patch 1.11.0 (20-Jun-2006): The tooltip for this talent has been adjusted to indicate it only works on normal melee swings.
Вовхэд:
Furthermore, you need to remember Flurry has only 3 charges when it triggers, and the charges are only used on melee auto attack so therefore TG with its slower swing time will result in the haste effect having a higher uptime.
Всё работает правильно.