Q:
Arms -> Furious
A:
An adrenaline strike is a “piece” of the burst gauge granted to you when you land an attack on an enemy. I’m not sure how many strikes it takes to fill a single bar, but landing a critical hit will grant an additional “piece” and therefore fill the gauge faster.
Thank you.
I’m not sure how many strikes it takes to fill a single bar
It takes 10 strikes to fill 1 bar. Read here: http://wiki.guildwars2.com/wiki/Adrenaline