Nemesis days help

In the recent breeding event for guaranteed fire legendaries I got enough lucifire the helltasers to get her to rank 2 with some cells leftover. I also got llum the magical matriarch and Warthak the mountain splitter from their respective events a couple months ago. I haven’t ranked lucifire in anticipation of the next Legendary overlords event, but would it be worth it to rank her and put runes on all of my nemesis monsters for the nemesis survival dungeon even if I won’t make it very far? Or would it be better to just pass the dungeon and not waste the runes or cells? Also should I rank up my llum or warthak at all?