Deadmines came out first, and thus is referred to as “DM”.
Dire Maul is referred to as DM E, DM W, & DM N respectively.
Calling Deadmines “VC” is incorrect. You don’t call Stratholme “RD”, or Molten Core “Rag”. So why would you call Deadmines “VC”?
If you want to avoid all confusion altogether, just spend the few seconds it requires to press 6-7 more keys and just write out the words. Just please stop blatantly calling Deadmines by the wrong acronym.