[x] change damage reduction from a stat to behaving more like range: light armor reduces damage by 20%, medium by 35%, and heavy by 50%. Each armor grade has an associated stat penalty, like range.
[x] remove defense stat - will decide on a different 5th stat later
[x] change each stat to be linear increases - each point increases something by 1%.
[x] rebalance equipment and stat totals accordingly
Diminishing returns are easy to balance, but make it hard to understand the correlation between stat points in to benefits out.