It seems that each

• Master of Calligraphy - Circle
• Master of Calligraphy - Triangle
• Master of Calligraphy - Square

is represented by exactly one quest in one zone
Although i am only missing one, i get the others suggested too.
It seems that in your code all quests fulfill all subcriteria, which looks wrong.

Shouldn't that be more like

		-- Circle, Square, Triangle
		{name = "Master Calligrapher", id = 13512, criteriaType = "QUESTS", criteria = 
			{{55340, 55342}, 
			{55264, 55343}, 
			{55341, 55344}}},

Horde:

Nazmir Horde Circle 55342
Voldun Horde Square 55343
Zuldazar Horde Triangle 55344

Alliance:
Circle: Tiragarde Sound, Vigil Hill (57, 62) 55340
Square: Drustvar, Fallhaven (56, 34) 55264
Triangle: Stormsong Valley, Fort Daelin (35, 38) 55341

Thanks for your detailed report.
When I added this achievement I didn't know the horde ids and I play only alliance myself.
Will update it.