A fix for this game mode in efc limit to how may of a card of that type can be in your deck.
as you know these cards are limited up to a point aloud in efc.
Ymirah Cr , Tiwi Ld , El Gascaro , Quetzal
limit it to only 1-2 aloud in a deck maken you have to use other cards from the other zones also cutting down on how often you aloud to get these cards.
so far what i can think of is limited
1-2 Chocomuscle ring cards in a deck at a time. still no banned list but a limitation to how many from a league can be used would work really well.
Personally, aside from matchmaking and points, some kind of list needs to be drafted up of like the mega op cards, op cards, from each clan (there won't be many, I'd say an average of 5 at a guess) then sort them out into zones theyre allowed up to.
For example, frozn have ymirah and kalindra as mega op, and ruru and tormentah as op (there may be others) and ymirah kalindra should be limited to the 1st zone, whilst the op ones, depending on how powerful they are, zones ahead of them. In this way you could single out the more op cards, of course there will be debate on some, but the majority will be near enough correct.
You could recruit players like you did last time (personally I wouldn't mind spending some time to determine the more op cards and having staff deciding on zones, but more input would be needed definitely)