Guild Wars 2

This set has this effects:

(1): +25 Power
(2): 5% chance to cause your next attack to steal health when hit. (Cooldown: 15s)
(3): +50 Power
(4): Your next attack after using your healing skill steals health.
(5): +90 Power
(6): You become mist when you fall below 10% health. (Cooldown: 60s)

But the last one seems not working, i’v tried reaching 10% of my health but nothing happens.

All that happens is that you lose all skills for 3 seconds. But there is no invulnerability as mist form should provide: “Morph into an invulnerable, vaporous mist for a brief time.”.