That's pretty much true for all teamwork-based games, really. A group of friends with organized plans and voice chat will almost always beat a group of randoms, barring massive skill gaps.
What's the major difference in the competitive matchmaking though, for someone who hasn't looked at the game itself in a while? Are there different balance changes made to the game to compensate for the idea that things are intentionally competitive and structured? An ability to queue up by preferred classes/roles?