The Problem is Office 2013 itself. The font-rendering system inside Office Apps bypasses every OS-setting and therefore this issue is unfixable.
Also it falls back to grayscale ( blurry or fuzzy , renders only black pixels , look depends on the scaling ) font rendering instead of RGB/BGR Cleartype ( always readable because it renders every Pixel ) which Microsoft uses on Windows Vista/7/8*.
Also DirectWrite is used fo Office 2013 ( and Metro in 8/.1) while Cleartype RGB/BGR positions fonts "free" while DWrite positions fonts via the GraphicsCard ( think of 3D Aero Rendering for fonts ), depending on the speed and capabilities of the GPU and
its driver this can lead to "lags" while typing, as every single font needs to be calculated on "how to position" it on screen.
The Hardware Positioning in Office 2013 can be circumvented via Words/Excels/etc Options. But the grayscaling renderer can not be avoided, so definitive there will always be a noticeable difference from ealierer Office Experiences.
As Microsoft is releasing constantly Gigabytes worth on updates for this messy App Collection I have hopes it might get better over time, at least it started to not look *that bad* any longer on my machines compared to the versions of one year ago.
*And one word to Windows 8/.1 :
The very same font-rendering is used on the "metro"-side of Windows 8/.1 , this looks as bad as Office 2013. On the Desktop-side this problem is absent, because it uses the font-rendering used under Vista/7 - so
as long as User skip and avoid "Modern Apps" , they wont notice it.
For Office Needs I recommend Office 2010 under Win8/.1 which will look perfect beccause it obeys Desktop Cleartype Settings; while version 2013does not as outlined above .
Modern Apps/ "Metro" renders in grayscale, Desktop in RGB/BGR