Ok got my head around the scaling a bit now, it feels like it affects your attack power more than your defence, up to a certain threshold?
I dropped all my offensive charms for defensive ones increasing resistances, including the mix flask. I was already using some good heavy armour but swapped in some marginally better pieces here and there and the difference was quite substantial, I went into a boss that was hitting me for 70-80% at times and was able to suck up a lot more punishment, I did it only 2 attempts later. The damage loss isn't even that bad, say 10-15% less for what feels like a 30-40% gain in defence, and each upgrade to the blessing is adding another 5% attack back on.