I did both rematch ragnaroks (the Kyuki one went horrible cause the ambush fail left me with only 3 kami standing so I haven't uploaded it).
Here's the Mastema one (with some slight mistakes like kami lineup but i still won)
i'm capable of clearing it without an elixir and it's still difficult for me (this is with Ares, Acala, Awakened Svarog, and Dakki as in FOUR SSR)
it's slightly luck based if you get hit by her raging nuke, but other than that, you need to have a lot of damage (and hope your debuffing doesn't fail to stick like ambush did to me once)