Have a strong frontline with two tanks or a strong tank in your team, maybe johanna, Anub, Muradin, Sonya, Rexxar. Switch around it works quite good.

Get a strong burst damage dealer like Kael Thas, Jaina or go for Kerrigan, Butcher, Tychus, Raynor, Valla.

A Strong bursty support or sustainable support with crowd control or mobility. Monk, Reghar, Uther, Medic when she comes out, maybe even start going dual support with Tyrande or Brightwing in the mix.

Specialist: Anything works, try it out depending on other role picks. Strong push/AOE dmg, Azmodan, Murky, Gazlowe, Zagara, Nazeebo CC, Nazeebo, Murky, Gazlowe, Zagara. Feel free to test out with your friends

Just keep that focus on symbiote on Nova to make her excel all around the map helping the whole team and instakill and soak xp. GL HF and Good night =)