OP is indeed misinformed, *however* The Characters OP listed are still getting similar Damage Reduction from Armor regardless of the fact that the threshold was lowered.

On live:

Tracer’s Pistol bullet of 6 damage does not surpass 10 damage, so it’s reduced by half, For a total of 3 damage.

On Ptr:

Tracer Pistol’s bullet of 6 damage meets the threshold of 6, and so is reduced by 3 points, for a total of 3 damage.

Exactly the same.

There is a difference however that Tracer can deal more damage with Headshots, assuming she is close enough to get the full 6 damage of her bullets. With the new armor rating she can deal 9 damage with a headshot over 6 on live.

For other heroes, the math checks out like so:

Sombra - Exceeds the damage threshold, deals -3 damage, for a total of 5.

+1 damage per bullet over live.

Reaper - exceeds the damage threshold, 7 damage per pellet, deals -3 for a total of 4 per pellet.

Supposedly Overwatch uses fractions, so that’s hilariously a half a point of additional damage over live.

This is more a nerf to slow healing such as that from Lucio’s Aura or Inspire when used on Armoured targets under fire more than anything else.