Who to support?

On my HE team, which I mainly use, I have +7 Reinhardt (+atk -res), +1 Sigurd (+hp -res), +1 Groom Marth, and Elise (+atk -res). I can even replace Marth with +2 Camus. Which hero should I summoner support with? I am looking for best benefit and Reinhardt is the current support.
Thanks