When you cast a spell, gcd is triggered.
As far as i'm aware gcd is haste capped: minimum of .6 sec ~.
When your spell resets a spell that is tied to the gcd, you'll have to wait until the gcd triggered from your first spell is finished.
When you hammer a spell that is not ready (which would trigger gcd), and you are currently off gcd you'll trigger a "fake" gcd of 0.2 seconds or so this is a failure response to the server
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