In my opinion I'd go with a team that goes well against the teams you fight in GNW, if that makes sense - like if everyone in enemy group is Earth and uses the shield, go with GNW Kank, Ignite from Fire or Paralyze from Lightning, and other debuffers. That's an extreme example but it makes sense, sorta. Or if you know you're going to be in a field with lots of low-damage revivers so you supply the area damage with fire's Dragon Flame. It all depends on a bunch of different factors and honestly it's a crapshoot XD

But Scarlet... he's awesome for pretty much everywhere. I've been fire from day 1 (Lightning for a day, wind for a day) and I have very few complaints.