We don't know for sure. From their own coverage, headshots (helmets/armour notwithstanding) are always lethal and a few body shots take an enemy down. Its highly doubtful we'll see the bullet-sponges of Division. It feels to me like GRW wants tactical takedowns, which is basically impossible with bullet sponge or "RPG" enemies.
Well, those who played the alpha in France, can you comment on what your personal experience was?
Is it like Vegas where you unload a full mag on the enemy, blood splurging everywhere but he still manage to kill you with a magic bullet even though the weapon was pointing to the floor?
or
Was it more realistic like said a couple of post below.