They’re two different problems imo so its worth bringing up both.
40 man queue syncers just need to be banned. 1 month, then 6 months, then perma. Gaming the queues to get an unfair advantage already gets you banned (eventually, when they can be bothered) in rated arena and rbgs, so naturally it should occur in Epic bgs too. It would be a joke to detect, too. Literally just take every single player above 750 or so honour level and track how often they decline queues. The average player probably declines maybe 1 out of 10 or 1 out of 20 bg queue pops. These guys decline, if Larkus’s stream is any estimate, 50-75% of their queue pops. Just ban em. They’re the yobs of WoW.
As for regular random bgs, a 5 man premade is a different problem in the fact that its actually allowed by the game, but still ruins the game. Some people want queues to be limited to only 2 people or even only solo queue, which personally I think is crazy for an MMO. I think an easier solution is to just give premades a stacking penalty - a reverse of that LFR buff you get from wiping. Queue with 3 players? 10% reduced health and damage done. Queue with 4? 20%, queue with 5? 30%.
This would offset the fact that they outgear everyone by queueing 10-20x more than the average player and would offset the fact that they bring every consumable possible.