Significant performance issue with high dpi

[Uwe]

we hope that this will mitigate the bad render performance.

I would be surprised if this would be the case. In the end the raster paint engine has to fill significantly more pixels, where the majority will be found somehow by interpolating - what is simply way more expensive.
IMHO your options are not to enable AA_EnableHighDpiScaling or to avoid the raster paint engine.

HTH,
Uwe