Guild Wars 2

Damaging on crit sigils like air or fire are causing rangers to be revealed when they proc on hunter’s shot. The sigils do not reveal thieves when they proc on cloak and dagger.

Can’t reproduce on the golems in hotm.
Even when both sigils proc on hunter’s shot I get stealth.

http://youtu.be/JgD_4_OI1gU

It seems like you are shooting at the golem in the back, your arrow pierces the first golem, procs Sigil of Air on it, then hits the 2nd golem and stealth you. The Air proc only then actually does damage and reveals you. If Air procs on the golem you are actually targeting, everything works fine.