I think OP means designer as in designer vs. niche, i.e. Burberry vs. Le Labo. Not designer as in "producer of fragrances."
That being said, the modern bit kind of throws me for a loop. I'm going to go ahead and say Égoïste by Chanel. I cannot, for the life of me, think of anything near a masterpiece that has been produced recently by a designer firm. There are a few women's scents that spring to mind... I guess that speaks to a larger truth about my tastes in general: I think almost all modern "men's" fragrances (1990s-2013) are just terrible.
Edit: Saw Dior Homme listed above. There you are!