Bad batch of pads is possible though unlikely
Do you recall the rotor surface condition?
- all even silvery grey (normal brake layer xfer)
- even coloring but some bright silver race tracks
- dark bluish annular bands at various rotor radii
Im still on stock rotors. My tech said they would make it one more round. Mind you he is a Mercedes tech who has his own shop with his son so I trust his judgement.