It seems they've changed their minds. Blizzard revealedthat they've restored the FOV slider in the latest build of the game.
The initial plan was to have a fixed FOV of 60 at 16:9, with a horizontal FOV of 92. The idea was that having no option to switch would prevent... actually, I'm still not sure what the rationale was. I'll let the studio explain itself.
“The rationale here is that we want to avoid creating a situation of "Haves and Have-Nots," where those who are aware of the slider are able to gain an advantage over those who aren't,” explainedat the time. “Instead, we'd rather develop towards a unified FOV that feels good across the board. Aiming preferences, viewmodels, dizziness, nausea—these are all factors we considered when designing the current FOV and will remain sensitive and very open to as testing continues.”
Irrelevant now, anyway, since the idea appears to have been binned. The Overwatch Beta is set for release