GA pilot reported entering CHD tower controlled traffic pattern 2;300 feet as published along with converging helicopter at published altitude of 1;900 feet; resulted in evasive action to avoid an NMAC. Pilot reported the procedure is unsafe and should be reviewed.

Narrative

I entered the traffic pattern at 2;300 feet and proceeded on downwind. A helicopter was transitioning from the north for the charlie pattern at 1;900 feet. They are asked by ATC to report north point and proceed across midfield to the charlie pattern. My vector and the helicopter's vector was the same minus the 400 feet separation (additionally I put my aircraft in a slow climb to create more separation for safety because we had not visually located each other yet). The helicopter was slow to locate me and call traffic in sight and yet the tower was (I feel) correct in the traffic scenario here. What feels unsafe to me is that separation (not the controlling action). It was recently changed at CHD after a fatal incident and I think it still needs to be reviewed. The mix of the charlie pattern and the north entry (downwind) along with the 2;300 Aircraft X / 1900 Aircraft Y feels unsafe to me. I hope this is something that the FAA can review in the future. Aircraft X pilots at a training-heavy airports are simply not going to maintain a strict adherence to TPA (traffic pattern) for Aircraft X in the downwind. Pilots and students will get complacent (and/or be in the midst of learning - both are human) and start an early descent and helicopters varying their approach TPA will coincide.