Guild Wars 2

I’m working on a build for my necro on WvW and I though how cool would be combining Superior Sigil of Nullification on my main hand, and Superior Sigil of Purity on my off hand. But someone told me "Once one of the sigils’s effect prock, both of them will get in cooldown ’cause all “% chance on critical” sigils share theyr cooldown".

Is it true or not?

http://wiki.guildwars2.com/wiki/Sigil#Mechanics