STM32F4 - DMA with bigger steps
As far as I know the STM32F4's DMA controller cannot do what you want. DMA can feed the DAC much faster than interrupt driven software (up to 10.5 Msps) so you might not need to skip samples anyway. 

If DMA is not fast enough then the classical solution is to make multiple copies of your waveform, each with half as many samples as the previous one. This will use a maximum of twice as much sample memory (1 + 1/2 + 1/4 + 1/8 etc). If you have several waveforms that take up a lot of space then you might not have enough memory to store all the higher octaves. However if you only need to play one waveform at a time then you may still have enough RAM to precompute and store the octave(s) required for just the current waveform.