How to approach engagements as Echo?

I've had success with Duplicate - beating S76 in a 1v1, rezzing the Junkrat on my team into a triple kill with Riptire, but I haven't yet quite figured out where Echo fits into team fights when not in Duplicate (or when duplicating an unfamiliar hero).

Since I don't know how to play every hero, my options for Duplicate are a little limited.