Last I checked Blizzard wasn't a government entity or bank, so they are working like the rest of us. Hell, I work adjacent to government and banks and I'm working today.
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Major is where I put Christmas, because otherwise that would make Christmas a Legendary holiday if MLK was on par. The only places that close for MLK are Banks and Government offices. Everything else is open on MLK day. Even Thanksgiving is above MLK as well in terms of what is open/closed.
I'm okay with the patch being tomorrow as my BLP just reset and I'm down to the final 4 for my spec and one of them is my BiS that I want so I can have fucking self healing.