I've been doing heroic VH for weeks straight now in search of this recipe. While it's possible that I am just getting unlucky, it seems hard to believe at this point. I see the patterns in all other dungeons drop frequently on all my characters. If someone can confirm that they have seen this pattern recently, I might just keep trying. But I thought I'd make a post on the off chance that I'm not the only one who has noticed this being the one pattern that seems to not exist.
I have the same problem with Design: Infused Twilight Opal from Anub'arak in Azjol-Nerub. I've been running this dungeon almost daily for like 3 weeks, but the design just won't drop for me. All other dungeons took no more than a few runs to get their respective designs.