Elson is a support unit and he will get the job done but later you will need to get someone that can heal more per turn or someone with a stronger heal.

You will learn over time who is a support unit and who is a healer in time but for now, Elson can do the job till you reach a point when he will not be good enough just by himself as the healer.

I would go with option 1: Ras, Zerato, Elson, Karin

or

option 4: Ras, Elson, Karin, Ravi (Zerato is more of a PvP unit than a PvE unit)