What are the roles that can best carry a team by yourself? Healer, then melee dps?

As ranged (bard) I feel like I'm all burst with relatively poor sustained dps to pressure, so if I get a bad melee dps for example, it's extremely difficult to find a kill window to capitalize on my burst, and the match pretty much goes nowhere. Just trying to save myself the most frustration - let's assume I'm equally good at all.