The only shrines that I've found that have been "too difficult" are the "Major" battle shrines, and those are incredibly out of the way.
Well I ended up at a "moderate test of strength" and I have four hearts and it was nuts.
My 12 weapon was doing no damage and every hit was a one shot. I managed anyway to get it down to a sliver of health but then the thing started zapping me from a distance and it was impossible to get close to it without being one shot by the zap.