IMHO Clarissa >> Malosi. Even after nerf, she is still poisonous GM, so I would chase her. That being said, new costumes are coming and will be likely out in May (as new patches are rolled out on monthly basis, usually towards the end of the month) which has double effect:
Positive: You have shot at getting something new for 3* and 4*
Negative: Dilutes pool of 5* you want, unless they are featured (but then again Magni, Sartana are still desired).
I would wait. Of course option number three is to pull in Valhalla (what I will do if Alfrike will be featured) or Atlantis (GM should be there, but so will be Atomos…). But from pure HoTM view, waiting for Clarissa is better.
Maybe use your keys today since they are all single pull, keep your gems for atlantis. Next month there might have new costumes heroes so that means less chances for joon vivi and lianna.
I did my pulls (had 5) with basically the same situation as you (hoping for Malosi) and got an Elena costume. Not sure how I feel about her. I did get Lady Woolerton on a lucky token though. I say wait for new costumes to appear, which is probably next month.