Surface mount devices are designed to go through an oven which is set up for the board that they occupy to travel through at a speed and temperature that suits the product and does not overheat the devices and stays within the maximum heat and time periods that a device can withstand while still melting the solder paste. When using a proper de-soldering/removal unit like a Danotherm hot air station, heat is blown directly onto the legs and pads of the device for a short time and then picked up with the vacuum head. The time depends on the device and ground plane etc transferring heat away etc.
Your method may work better if you look at the tracks and pads that are on the board that you have already removed a chip from and see if there is any way to cut the tracks close to the actual pads so that there is less copper to disperse the heat and hopefully make the chip removal that much faster. Apart from the thermal shock damage there could be physical/mechanical shock or maybe your antistatic wristband has broke (it happens).
Good luck with your project
