Do non-boss enemies have weak spots where they get extra damage dealt to them?

Solution 1:

Yes and no; nothing really has a weak spot for non-amputation damage except those with yellow, glowing cartilage, like the large bulbous yellow spots on Exploders and Tentacles. Exploders die in one shot to the explosive sack. Tentacles and anything with a large yellow, glowing cartilage section have the yellow bit as a "weak point" which is usually the only part that can take damage, but you probably consider those "bosses". This is just the same as it's been since Dead Space 1.

Limbs are the obvious "weak spot" but not all limb removals do the same damage; specifically, head removals do less than removing legs or "weapon" limbs. Removing all bladed/weapon-like limbs will generally kill any necromorph even if 2 limb removals otherwise wouldn't be enough; once a necromorph stops being able to attack it will "die" immediately, except the new Wasters which can sprout tentacles at the waist after "death". Depending on the enemy, leg shots may be much more useful, as slowing down some enemies like Slashers renders them much weaker. None of this matters much to javelin gun users though.

There aren't "strong" points on most non-boss enemies, but there are some spots where shooting them isn't a good idea:

• Shooting Pregnants in the body is a really bad idea, even with the Jav gun. Bad enough to be worth switching to another gun. Though javelin explosions (and other explosives) are ideal at cleaning up the Swarmers the Pregants usually release.
• Wasters, the guys with picks and snow coats who sprout tentacles from the waist, should have their legs severed, shooting them in the chest/removing their arms often results in them sprouting extra tentacles, forcing you to waste more ammo and possibly take more damage.
• Guardians can't be body shot, unlike most nercomorphs, even with the javelin gun. You'll need to cut off their tentacles, though if you're using an explosive/AOE module with the jav gun you can sever their limbs that way.
• Dividers should be shot in the limbs, not chest, since the chest is lifeless after they divide. AOE/explosions are recommended.
• If memory serves me, and Dead Space 3 hasn't changed this, head shots with the javelin on necromorphs is actually less effective than a body shot; the head just comes clean off, little/no staggering happens, and the necromorph isn't set up for a shock/explosion combo (if that's still a thing). I don't have the jav gun yet in DS3 though, so I could be wrong, that's just what I recall form Dead Space 2.
• Feeders are apparently weak to head shots, unlike most other necromorphs.

Human enemies go down extremely fast from head shots; the otherwise useless SMG for example seems to take them down in a single hit. I don't think limbs are a "strong point" for humans, but it's generally ill-advised to aim for humans' limbs anyway, since their heads are relatively stationary (much easier to hit than any Necromorph's limbs), are always in clear view, and headshots take them down so insanely quickly.