With the new Icescale armor of brutality I don't see any reason to use mythic anymore. The set bonus makes a huge difference compared to past event sets. These are the stat differences when comparing the full sets:

Mythic: 8.16 crit higher, 11.1 damage and 15.4 dps more

Icescale brut: 175 health and 112 armor more

As of now only the crit makes mythic armor better and I can lose that much by switching pets. The small damage increase isn't worth the health and armor loss at all anymore.