Onatel or Vivica. Need help on defence team

I pulled Onatel last month and have her almost to final ascension. Currently, in upper platinum tier, and use Li Xiu as my tank. I wanted to replace her with Onatel in a couple weeks.

However last night I pulled Vivica from TC20. I don’t have any other 5* healers but several 4*( Rigard, Kiril, BT, Sabina). My question is which in your opinions is better to fully ascend? I have 9 darts so maybe the runner-up won’t have to wait that long.

Another consideration is my planned defense team:

Evelyn-Isarnia-Onatel- Khiona-Mitsuko ( I don’t have any big hitting snipers)

Alternatively with a healer
Evelyn - Rigard/BT - Onatel- Khiona-Mitsuko

If I were to replace Onatel with Vivica in that lineup I’d have 2 slows which I don’t like. Plus none of the others are a true tank. I would drop the other healers obviously so the best I can think of then for the defense is:

Evelyn - Isarnia- Khiona- Mitsuko- Vivica ->again 2 slows=uugh

Suggestions? Thanks in advance.