The DMA stuff is way over my head. I thought that was used to interface parallel RAM? What would I get out of what you're describing that I don't already get just by triggering an interrupt ever 10ms and reading the 4 ADCs only then?
DMA is your delivery guy. You can use it with many peripherals, accessing parallel RAM is only one example.
What are the benefits? Less processing power used for background tasks like reading the pot values, more power (cycles per one sample) for processing audio data or other important things, like an LFO for example.
Simplifying the process a little bit, because there are also interrupt priority levels and stack operations - what your program needs to do now is to break every 10ms, jump to the timer ISR, start conversion, wait until its done, read the result, change the channel, repeat it 3 times.
Using DMA+ADC the converter works in background and fully automatic doing all four conversion and storing them. When they are ready, the delivery guy knocks at your door (DMA interrupt) and serves you all the data.
It's just one way to optimize the performance and make use of the features the PIC32 has onboard.