We've had this discussion countless times in the past. The end result of requirements is this: people get confused and get disqualified for using illegal decks. Vets and newbies alike.
If you're in tournaments to have fun, you won't cop out on the deckbuilding rules.
If you're in tournaments to win, a duo/trio is capable of kicking any mono in the face now that Discord is out.
Duos and trios are only marginally better against discord than monos. Trios especially are hurt by the fact that their quanta bases are more fragile to begin with.
Why not just say that people have to use 6 cards from at least 2 elements? Simple and requires actual duos.