so whenever i enter GDS and then to move onto the monster i leave GDS. But I don't actually move because the creature is in my way. is this supposed to happen?
The word stance is defined as standing without moving (althoug I may be wrong here). Therefore....
clicking the special and closing in for melee is definitely the wrong approach!
Simple solution: click the special and wait for the monster to close in for melee. And this is defined as tanking by some folks (gosh how I hate this term in MMO´s!).
And before the next misunderstanding occurs: No it is not possible to move around and remain either in GDS or LDS. Such a special does not exist. A lesser, simplyfied form exists although, it´s called parrying.
One problem may occur, when you move, the monster is very close and you hit GDS while still moving. That results in a lean and even several tries to enter GDS ate unsuccessful, since the last command, the moving, overrides that.
The operative words are "Defensive" as in brace yourself (sword and shield), and "Stance" as in plant your feet in the ground and don't move.
Or if you refer,
The Defensive Stance is a cautious back-footed stance that allows warriors to react more efficiently to incoming attacks, and better utilize the sheer immensity of armor available.
Any and all movement will break the Stance, cancel it and reseting the cooldown/Skill timer.