Yanfly's Enemy Levels plugin and it's Custom Parameter Formula function. The formula I'm using looks like this:
<Custom Parameter stat Formula>
base * (1 + (level – 1) * rate) + (flat * (level – 1))
</Custom Parameter stat Formula>
base * (1 + (level – 1) * rate) + (flat * (level – 1))
</Custom Parameter stat Formula>
<Custom Parameter stat Formula>
33 * (1 + (level – 1) * 0.5) + (-15.04 * (level – 1))
</Custom Parameter stat Formula>
33 * (1 + (level – 1) * 0.5) + (-15.04 * (level – 1))
</Custom Parameter stat Formula>