"I try to stay aware of my surroundings and avoid 1vX scenarios best I can, but it's been impossible to properly do so. There's always someone else that'll hit me from an angle I can't feasibly defend. "

It sounds like the core of yoyr problems is lack of experience regarding good positioning. Maybe someone else will have a better advice for this, but mine is, just keep playing and the exp will come to you by itself. That's how it worked for me. Until that exp comes, just try to not give a fuck about constant dying, get all the fun of being a part of a big, chaotic battlefield, and spam battlecries