Guild Wars 2

Does anyone know how does the different armor classes work with the toughness stat in PVP?
Say I’m using an amulet with +900 Toughness, will a light armor class (ele / necro / etc) be hit harder than a heavy one (war / guard) wearing the same amulet?

More clearly, is there a difference between an ele at 2800 armor and a guard at 2800 armor or is the entire difference between armor classes is only in the base number of the toughness stat?

yes, eles with 2800 toughness are hit harder then warriors with 2800 toughness . The thing is toughness increases armor and armor is what used for damage reduction. So eles with 2800 armor are hit equally hard as warriors with 2800 armor.