The easiest "Run and slay" ways to get Pattern: Rich Purple Silk Shirt

I wonder what is the “easy” way to farm it with not much effort besides one shot or easy to kill mobs that are densely grouped? If there is such a way (I have no idea where to farm it beside the fact that is it said on other websites that is a super rare drop.
P. S. This is my first post on World of Warcraft Official Forum so please be gentle on me. Thanks :slight_smile: