Is ADC over-voltage protection needed when input isn't external?
You have a 30V supply and an 11:1 divider.  So as long as &quot;some internal voltage signal&quot; is not so large that it causes OA1 to malfunction, you should not get a value greater than 2.73V at the ADC input.  If the ADC can accept voltages in the range of 0V to 2.73V, then you don't need additional protection.
I would note that the output of your divider has an impedance of 909 ohms, which is quite high if you are feeding an ADC.  You will probably get better ADC readings if you add a small capacitor (10nF to 100nF) in parallel with R2.  Alternatively you could put the voltage divider before the divider, and use a 3.3V supply for the op amp.