Damage types and class favouring

Slashing, Piercing, Blunt, Projectile, Magical (and all the elements, of course!)... just how much do they matter? I notice them often but rarely notice any major difference against enemies. I only ask because at the moment, people often complain that a class is favoured or disregarded by the system. Would balancing be made more effective by simply making it so some damage types are less effective against certain enemies? That way when you go from enemy to enemy, particularly in raids where you are fairly restricted, it would make much more of an impact for certain type of weapon.

I basically got inspired by reading all this stuff about how some ogre apparently spams AOE and therefore archers are a requirement. So, for example, Lancers feeling underwanted? Decrease defences of certain major mobs (ogre?) to piercing attacks. Archers too effective when dealing with AOE enemies? Don't adjust archers, adjust the mob! The sensible change would be to increase their defences towards projectile damage types rather than screwing around with the archer class.

Basically, I can't help but feel this game would really benefit by having certain mobs that are notably weak versus certain weapons, while notably strong against others. That way every class will always have a few mobs out there that will increase the demand for that type of class. :) Subsequently, people should hopefully always find a use for themselves and a good place to level varying party types.

Personally, it seems logical for me. Some rock-hard enemies shouldn't really suffer at all from arrows and swords, but a heavy mace should really piss them off. Likewise, sometimes a pile of goo won't care what it's attacked with, until magic comes along (hi, flans) and of course a fat, leathery skinned enemy with a lot of blubber wouldn't be very weak to a hammer, but it would feel the pain when it's leathery exterior got a few slashes and piercings. Some might have a rock hard lower body but a weak out-of-reach spot, in which case arrows are ideal. Finally, of course, some would just be... normal. :) Human-like, if you will. And everything will hurt them.

Caster here so I'll just comment on the magical attacks.
On mobs resistant to the element, I get more resists and a reduction in damage, amount depending on mob.
On mobs weak to the element, I get a bonus in damage.
E.g. Casting fire on bomb > Casting ice on bomb
On mobs strong to the element, it can absorb the damage as HP.
E.g. Flans (Depends on color) - Cast fire when they are red and they absorb it.

The effect is pretty noticeable for magic.

I figure the same applies to melee damage.
Skeletons are typically weak to blunt so you can probably test damage with that.

That said, I think people tend to forget that all melees have a ranged attack as well in FFXIV. Lancers can throw javelins and Puglists can throw chakrams. Less efficient for sure but last I asked, the damage on the Ogre isn't that much lower than a typical archer shot.

I doubt a lot of melees actually use these attacks though.