Q: 2018 MBP overheating using external monitor

I have been using this newly upgraded MBP 2018 (i7 2.6GHz, 32GB) for few months now. It is always over-heated while an external monitor plugged.

I have tried the original Apple HDMI adaptor, the 3rd party adaptors, a std. Dell WD15 USB-C docking station. Also tried various monitors, 4K monitor, a simple 1080p old monitor. after few months trying, it seems not the problem of the adapter or monitor, but really the problem of over-heating while the dGPU is using.It works perfectly connected to Dell WD15 docking, for power charging and USB etc. (as long as no monitor connected). The dGPU only kicks in when needed. the idle CPU temp is normal, and system remains completely silent (with CPU fans around 1000~2000rpm)

However, things get completely worse when connecting an external display. The dGPU kicks in, as "always-on" mode, heats the idle CPU temp up from 45° C to 65° C (I repeat: idle). It doesn't matter if it is over HDMI / USB-C, if it is a mirrored / extended desktop or if it is 1080p / 4K that is being driven. If I leave it on (as idle) for a while, or combining this with some light development work, the CPU easily reaches 75° to 90° C and the keyboard starts to radiate uncomfortable warmth to your fingers. The palm rest also gets warm up to the point where my palms start to sweat. The fans try to cool down the system and they speed up quickly up to the point where they become audible and start to really bother me.

Yes, I can and did get an external cooling pad under the MBP (for this 3000 USD laptop), but still no much improvement. actually it finally crash due to the heats today, while copying 1TB files between external HD.

What is really frustrating most is it is even worse than my 4.5 years old 2013 MBP 15, which has the similar design, like dGPU always kicks in while external monitor connected. However, I have never had this over-heating problem in the past 4.5 years.

I did see lots of people having the similar issues with 2018 MBP model, but after days and days research, it seems there is no any real solution for it, and the most feedback I got from my research is "return it back to Apple".

So, Apple, can you please help me? really don't want to go back to PC laptop after 5 years usage of MacBook.