Have you tried my "solution" ? Check it out in one of my comments.
Now I know that it's not W7 exclusive because you report the same issue with W8.1.
I said I wasn't going to upgrade to W10 but I finally did it because I needed to install a program that required that OS.
Does W8.1 have that "XP style" option to uncheck? If so, why don't you give it a try? It won't mess anything and you can go back and check it again if you find something wrong.
Like I said, I used to have W7 a few days ago but I went straight to W10 (I guess I'll never know what W8 and W8.1 were really like).
My suggestion, once again: try to uncheck that "XP style" option (if you have it) or upgrade to W10 for free.
W10 doesn't have that XP option and I assume it's hidden and unchecked (according to its behaviour when I use 125% font size).
I will always use that size because I hate tiny fonts. Also, I use font renderers to make fonts look like they should. I used GDIPP on W7 and now I'm using MacType on W10.
My biggest complaint for Microsoft has always been the awful and useless font rendering (ClearType *****).
So, in the mean time, while you wait for Apple to fix this (maybe they'll never do that) you can try my suggestions.
See ya!