Intensity: 62 Eh
The comp should work for an intensity that's a bit higher though. I didn't need the damage from Elf at all to get the kill in the end.
Loadout shown at the start. Rosalia can use Jingwei-Ekat-Newton instead for a fair bit higher damage but much worse consistency.
S-Rank Rosalia should work as well if you have decent Affix (since she does not get any damaging passive that applies to the Ult).
Rosalia ATK is 1138. Divine Key: +6% Physical