Something that might work - at least for paladin, not sure about shaman - is a rune that doesn’t specifically give you spell power “an increase to damage and healing from magic spells” ( 
) based on your strength, but exchanges your physical damage dealt for X% of damage from that source instead as Holy damage. Similar to how paladin in WoD had the Final Verdict talent(different than the current Final Verdict) to replace Templar’s Verdict, with Templar’s Verdict dealing 259% Physical Damage, and Final Verdict dealing 240%, but as Holy Damage instead of Physical.
It would likely have to be a significant decrease in flat damage, especially when you consider PvP - I don’t believe there’s any way to resist Holy damage specifically, unless abilities/talents/potions that give resistance to ALL magic do for Holy as well - and would probably have to be thoroughly tested before going live (and then nerfed into the ground repeatedly before it’s not considered “insanely OP”), but it at least makes sense from a thematic standpoint, and I at least think it’d have potential. I could very well be wrong, though.
Strength also increases block value, at a whopping 1 damage blocked per 20 strength at level 60.
Yeah, it’s not really worth mentioning, and a lot of people probably don’t even bother to remember this because it’s generally inconsequential.