The way I see it is… Health protects against all kinds of attacks: fire, ice, blunt, normal, piercing. So no matter what is trying to break through that barrier, it has a higher health to resist.
I only start to forge the specialized resistance after I start to get a drop-off in the marginal rate of return on the Health forging. That’s around 20+ forgings on the Health.
Another good question may be: barricades versus blockades.
From what I have seen, high level players do not use barricades, they use blockades. So before you spend a ton of money upgrading a barricade, and even more pearls forging it, you may wish to consider replacing it with a blockade.