I know it's probably out of convenience more than anything (re-using existing CS assets), but it's interesting to me that it was First Person at this stage and not Third. I've been wondering if I'd enjoy it better as an FPS as opposed to TPS.
As someone who has adopted it as a replacement for Battleborn, me too.
But even in Battleborn, certain abilities would pull the camera out to a third person perspective, because in first person you just wouldn't be able to see what you were doing otherwise.
I think playing around cover is better in third person, too. Have you noticed that jungle creeps and the characters have a different animation when shooting "around a corner"?
It seems MOBA mechanics benefit a lot from the improved awareness of a third person camera.