Brand new trailer brakes need to be barished in. I've only had to replace trailer brakes once out of my 4 trailers and that was due to cracking not wear. Believe it or not but you need to drive down the road several miles alternately activating the trailer brakes manually to wear them in. Lightly applied for some distance and then heavy applied for a few hundred feet (heat them up). Makes a huge difference.
However your description of full power with little braking seems like the brakes aren't properly adjusted either. I went from needing around 9 on the prodigy to get good breaking to 6 to have great breaking once Barnished in.