I don't know if these numbers are correct, but a 5% defense boost is almost irrelevant.
If you're playing medium load with 20% damage reduction, that's (1,05¹² = 1,79) or a whopping 15% extra absorbed damage after getting all Scadutree blessings. That's comparable to one of Blackguard's crabs or less than the Dragoncrest talisman... and it hardly makes up for enemies hitting thrice as hard, does it.
The cold truth of the matter is that Scadu fragments or not, when those incredibly annoying and long multi-attacks from all directions come at you, you better tap that B button and just pray to sweet young Miquella that you happen to have done so at the right time.
Or maybe build yourself like a fucking tank like the early DS1 meta, I don't know.