StanceSets didn't work with patch 3.3.0.
It is not longer possible to switch the weapon in combat. Blizzard has deactivate these function for addons. I'm so sorry but i think StanceSet is now waste.
This is a modified version of StanceSets which was originally written by capnbry, modified by Smuggles and Vorkosigan-ger.
This add-on allow you to quickly swap weapons, shield and ammo on a single key press, and cycles between two or three different weapons sets. Additionaly this add-on can have different weapons sets cycle for different stances and shapes.
Typing /stancesets will open the stance set configuration dialog. Drag and drop the weapons you want equipped for each set into the containers, starting from the left. If you want to make sure the first set is in your hands when you assume that stance / form, check the "Equip first on activate". If you do not have this checked, and the weapons in your hand match one of the sets from your new stance, no swap will occur. To remove a weapon, drag it off the slot.
Up to 3 sets of weapons can be available for each stance. To cycle through them, use "/stancesets next". The addon will loop around to the beginning after the last sets. If you don't have any matching set in your hand when you call "next(x)", the current active set will be put in your hands.
You can direct activate a set for the current stance with “/stancesets set1”, “/stancesets set2” or “/stancesets set3”. For alternate sets the function are not available. In this case you must use the “next2” or “next3” command. For the alternate sets use "/stancesets next2" or "/stancesets next3" to cycle through them.
The panel toggle and set cycle can be bound to a key combination. This is the better and faster way to change the set.