Is there a chart, or somewhere that explains how much (for example) strength is lost when you sync down 20 levels. Is it a percentage of the max amount that was on the gear, or item level?

Tried checking my gear in the instance and it just had a (S) next to it. Numbers were still the same.

Or do we need to buy level appropriate gear?

If it does scale would a level 30 gear with +3 strength be better than lvl 50 gear with +6 strength?