Aptotec PN532 shield power consumption
After some trial and error, I think I can answer this one myself.

The circuit schematic from the Seeed module is actually broken and the Apotec model is built almost identically. The PN532 chip has an SVDD output pin to power an optional security access module for cryptography support. In the Seeed design, this pin is connected to the 3.3V input voltage from the voltage regulator, which is simply wrong and the pin sinks an essential amount of current.