Does playing Overwatch make you feel like there's something in the water? Something that magically transforms you into a sniper demon, or conversely, a tottering watermelon with legs? You might be onto something. Force Gaming decided to test Overwatch's headshot hitboxes (that is, the area in which something counts as a hit as opposed to a miss), and he found them to be awfully generous:
Basically, Overwatch's hitboxes are significantly more forgiving than some other FPSes. This is especially true with projectile weapons like Hanzo's arrows, Genji's shuriken and Mei's icicle launcher. You can aim nearly a head's worth of space above a character's actual head and still pulp their precious brains into a gooey grey matter smoothie. There's also a lot of give on the sides of heads. Characters can be hidden around walls -- to the point that you cannot see them -- and still fall to a well-placed/randomly flung shuriken.
The hitboxes aren't quite as large when more traditional guns like McCree's revolver or Widowmaker's sniper rifle are doing the shooting, but they're still remarkably large.
While "2 hardcore 4 u" (or even "just hardcore enough for you") types might bemoan this design choice, it fits with Overwatch's overall goal of letting everyone feel like a winner sometimes. Blizzard has ever so slightly lowered the barrier to accomplishing the quintessential Badarse FPS Feat. Does that cheapen it? I suppose it depends on your perspective. To me, Overwatch is more interesting as a game of crazy strategies and wacky abilities than it is as a canvas for frighteningly accurate FPS artistes. I think generous headshot hitboxes matter less here than in other games.
At the same time, though, it kinda sucks to get killed by a shot that didn't even hit you. The other night I was in the middle of the best Widowmaker streak of my life, and somebody killed me while I was (I thought) safely behind cover. That's a fundamentally frustrating moment; they didn't earn that kill, I didn't deserve that death.
I feel like the best compromise would involve Blizzard offering separate competitive and/or quick play servers that required increased firing precision and, say, upped the server tick rate, another thing that sometimes allows missed shots to hit. The game would still default to the current settings, but for people who want a less forgiving experience, they could have their own playground. I'm sure Blizzard is monitoring people's reaction to all of this, so it could very well change.