I see no difference in the output numbers when I activate the shock and awe buff. Currently, at level 55, it gives me 141 spellpower, which almost doubles my total spellpower.
But I see no difference. Flash of light, holy shock, exorcism, holy light. Everything I have… there is no difference in the output with holy shock buff on or off.
it gives only spell dmg, not dmg and heal.
Ye, I discovered that shortly after writing on here. But I figured editing this would be cowardly. 
But ye… still feels underwhelming. Without the buff a exorcism crit was just under 800. With the buff, which essentially doubles my spellpower, the crit was almost 900.
So going from around 150 spellpower to around 300 increased the damage by around 100.
When I used sheath of light in addition, and put on seal of the crusader and a few bits of str gear, my combined spellpower for holy damage was just under 500. So 200 more spellpower.
And exorcism crit for 1k.
That’s around 350 extra spellpower for a power increase on my spells of around 15%… roughly speaking.