Those Areas mostly already have Metropolitans, but the problem is that once your in a MP game u tend to sometimes get huge amounts of devastation since u wil have drawn out wars. and even with a Fort and Metropolitan u wil only lose about 1 devastation per Year, but every 15 Years u can get in to a war giving u up to 40% devastationVery specific but in this case playing as orthodox Russia with Third Rome Consecrating Metropolitans will also give areas monthly ticking -devastation
So Just Fort's and Metropolitans seem to not be enough in the Last age
This Picture is after One war where 5 Great power's Teamed Russia, and Parts of Russia got Devastated since it was occupied for a long time