There is a 1 second global cooldown for all abilities. You can only perform one ability per second, be the ability itself instant cast, or a 0.6 second channel.
You may be able to activate 2 abilities in a row, but there will still be a 1 second gap between when they are executed.
You can fit a light attack, ability and a bash within 1 second, or close to it, but not two abilities.
Where the 0.6 seconds becomes relevant is in your ability to block. Instant cast abilities can be cast while holding block. Flurry will cause you to drop block for 0.6 seconds.