The approach climb gradient is based on OEI (2.1%) and for a two-engined aeroplane its usually the limiting between Approach and landing climb gradients.
You can also find the chart in the FCOM performance Dispatch.
My guess for not publishing a two engine gradient is because it's not the worst-case scenario. On most modern jets, a single-engine go-around is more than capable of doing 2.5% climb gradient.