Vcore is 1Vish, there are few
other voltages on Pi3 too.
You see four inductors near PMIC chip. Measure them all, should have life in there. Check for any damaged components under the microscope. Sometimes those tiny ceramic capacitors crack, and short to ground.
Anything get hot? One of my old Pi1's died when overloaded I/O pin with 4.5V instead of 3.3V, as result CPU started to cook.
Other dead Pi1 was result of PSU reversal
. Memory chip had the magic smoke escape.