Calwings posted... https://iili.io/HUuj8UN.jpg
I finally managed to complete world 3 of Simulated Universe with the default F2P core. I got really lucky on the way and got a benefit (can't remember if it was a blessing or a curio) that split incoming damage evenly across my whole team, so between that, the trailblazer's taunt, March 7th's shield, and Natasha's healing, I just went full turtle mode and eventually whittled the boss down. I nearly lost when I wasted my ults at the end of his phase 2 (not even knowing he had a phase 3 because I had never made it that far) but I managed to survive.
I'm not even going to touch world 4 until I can level my characters up more. I'm at TB Lv38, and I think you can unlock the next equilibrium at 40.
World 4 has a bunch of fire weak enemies from the looks of things, so you could probably run Fire TB/Nat/Asta/Himeko there and manage well enough, maybe download Dan for the boss to sub for Himeko, though I don't think that's really necessary.