The PCI-6052 has 16 analog inputs, with a maximum sampling rate of 200 Ks/s. Since you want to use 12 channels this means that the scan rate for each channel is going to be 200 /12 channels. You will see that this means each channel will will sample at a rate of 16.6kHZ, even if you use 2 boards to do this you will only get a sampling rate of 33kHz. Therefore, the limitation would not be with LabVIEW but with your DAQ device.
As far as sampling and writing to a file you can always you the AI functions and a write to spreadsheet file vi.