This has been discussed. Including in the quote you linked. So I'm not sure why you need to ask again.
"Q: Is Glyph of Disease any good?
A: It's useful for AOE, but far inferior to any of the available options particularly Scourge Strike, it comes out to be a dps loss since even though it's refreshing your diseases (And if you don't refresh right after a disease tick you will LOSE damage) it's also not doing any damage."
Perhaps i'm blind but couldn't find anything regarding "glyph of disease"? Is it a valid option to use instead of glyph of scourge strike?