Liva said it better than I could.
These 1 or 2 shot ranged kills may sound good as a fantasy in your head, but isn't conducive to fun gameplay and counter play.
If the dmg scale on ranged abilities were that high then they can just stop wasting time on developing any other combat mechanics.
I understand a 1 shot kill isn't far fetched in RL, but it just has no place in a game where the death mechanic isn't a very short respawn.
This game is taking a realistic approach to many things, but I highly doubt the combat is going to meet the same level of realism many here are projecting.
The combat likely won't be cartoony or super flashy like many games, but that's about the extent of the realism one should expect from combat interactions.