All three weapons are a grind.
For mythic you grind out the Alexandrite, repeat assaults, Ichor and nyzul isle tokens.
For relic you grind out currancy.
For empyrean you grind out a few NMs.
Out of those, Mythics and Relics (moreso mythics) are the biggest grinds. Yet at 85 and 90, Empyreans were better than their mythic counterparts (with a few exceptions like Kenkonken and Ryunohige) for melee. Why does an "ultimate weapon" thats stronger beat another "ultimate weapon" that takes significantly more time?
As I said before, this is SEs way of leveling the playing field, to make the time:reward ratio more sensible. This is the cockblock that will leave most empyrean holders at 85 or 90. And that's good, because empyreans are not-much-time:one-hell-of-a-reward compared to relics and empyreans.
I hope shit continues to get harder. I'm bored of grinding out easy mode. Abyssea is just grinding out the gear I'm missing still, I'm kinda over it and want a challenge again.