The problem with gradient meshes is that they are 2D grids that run all the way through the shape. Thus you can't add control points on one side of your mesh without adding a bunch of useless ones across the whole length or width. Each mesh segment has to be a 4-sided bezier patch. If you try to gradient mesh a curved shape, the mesh lines run at very awkward angles, it's often better to start straight and bend it only after subdivision. Diffusion curves solve all of these problems, and seem to have no obvious downsides.
I don't see how they would match the artist's intention any less, quite the opposite. You can alter any small part of the image without compromising the overall structure, and you can control spline tension through the blur radius. The only thing I would say is missing is the ability to skew the blur to be more intense on one side of the diffusion curve, thus creating asymmetrical gradients.
In tools like Illustrator gradient meshes are flattened to images anyway when exported to PDF. So if a technique like this was implemented, it wouldn't change the workflow at all. In fact, I expect to see this in Illustrator in the next two versions.
I can't find a source but I think gradient meshes are only flattened to images to handle old or buggy postscript implementations. Postscript 3 can handle them natively.
I don't see how they would match the artist's intention any less, quite the opposite. You can alter any small part of the image without compromising the overall structure, and you can control spline tension through the blur radius. The only thing I would say is missing is the ability to skew the blur to be more intense on one side of the diffusion curve, thus creating asymmetrical gradients.
In tools like Illustrator gradient meshes are flattened to images anyway when exported to PDF. So if a technique like this was implemented, it wouldn't change the workflow at all. In fact, I expect to see this in Illustrator in the next two versions.