I don't know why Blizzard just didn't change his spawn point to anywhere but there after realizing its a problem. That would instantly fix it.
I'd consider it griefing just because the sole reason you'd do it is to annoy others. You can't ban people for it though because A. Its easily preventable, you can just fly up there yourself. Something like wiping the raid in LFR or crashing the server is pretty unpreventable. B. you don't know who is actually griefing as others may be up there to avoid being griefed.