NorthSouth,
climb gradients are not a directly required function of OEI performance when considering PC2 in its purest form, but do become a factor when looking at the obstacle clearance requirements or IFR departures/missed approaches.
JAR/FAR 29 Cat A certification requirements express OEI performance in rates of climb, whereas the UK CAA used to require climb gardients for BCAR Group A certification. JAR OPS-3 and ICAO Annex 6 performance requirements mirror the Cat A requirements for PC1 and use elements of it for PC2.
Depending on the aircraft you operate, the Flight Manual may have graphs that allow you to calculate the climb gradients for Vtoss and/or Vy, which you can then use to confirm compliance with obstacle clearance or IFR requirements. It's a useful exercise to look at in any case; you may find the horizontal distances travelled somewhat eye watering!
To give an example for an aircraft with a typical Vy of 70 kts:
In the second segment, climbing at 150 ft/min, it covers 7090 ft for every 150 ft of climb. So, from 200 ft to 1000 ft it covers nearly 38000 ft, which is over 6 nm! (For info, I did not use Sine as the angle is so small!)
That same aircraft is climbing with a 2.1% gradient which is less than the usual minimum of 2.5% expected for a SID or missed approach procedure, so if flying IFR you would probably need to reduce the weight to increase the climb gradient.