I have a Lenovo Yoga 2 Pro which has a resolution of 3200 x 1800 which I run at 200% scaling.
I have just bought an Asus PB278Q which has a resolution of 2560 x 1440 which I run at 100% scaling, and which I want to use for development.
However, all content on the external display is blurry.
So I tried the option for setting one scaling of 100% for all displays and now the external display is sharp as it should be, but the internal display is obviously useless in desktop mode because everything is too small. I verified that the external display is being driven at the correct resolution via the monitor's own information option which says 2560 x 1440 at 60Hz (I was at least pleased that the Intel HD 4400 graphics were able to drive both displays at their proper resolution with 32-bit colour and at 60Hz). I have a fully updated version of Windows 8.1 Update 1.
So my guess is that Windows is rendering my external display off-screen at 200% and then crunching it down to 100% via bitmap processing.
Surely Microsoft have not implemented multiple display scaling like this? If they have then in my opinion it's useless, There is no way I can tolerate such blurriness on the external display at 100% scaling especially as I intend to use it mainly for development so clarity of text is important.
Can anyone help me fix this, or have Microsoft really made such a bad implementation of 'independent' scaling for separate displays?
Edit: Added comparison screenshots of external display showing File Explorer and Visual Studio 2013: