Oh ok; we’re talking about two different solutions (mine was similar to what you described at the end). Yeah, that sounds good. I like that a lot better than what CreateBillboard does. The only (minor) qualm I have with that approach is that you might get a tiny amount if rounding error because the world matrix is cancelling out the view orientation, which might possibly cause some alignment imperfections, and you wouldn’t want to do this operation on, say, hundreds of individual particles. But for scenes like the OP demoed, that should be just fine.
(An example of said alignment issues that I’ve encountered would be Z values differing just enough to throw off the depth stencil on multiple passes, resulting in lighting/texture banding.)