If you checked out The Balance Discord some time ago around ShB launch were patch notes specifically stated that blocking and parry has been nerfed, it was worked out that both mitigation were reduced by 5%. While my omega shield allowed me to block 30% of damage, basic maths land me with 25% damage reduction. As for 10% damage reduction, with exception to possibly deep dungeons and maybe eureka, in every day gameplay, I've not seen block below 15% DR.