1) Premades should be matched against premades. Groups of over 5 people (for WSG) and groups of over 7 people (for AB) - ie. if more than half of a BG is premade, they should be thrown in a separate queue, where they are queued against players with the same group size.
OR
2) Average ranking. Take the average rank of players that queue and match it with a similar average in the opposing faction.
OR
3) Keep all current mechanics, but introduce PvP Rank Brackets. ie. Rank 1-4 players in 1 queue. Rank 5-10. Rank 11+. This way casuals play with casuals, the hardcore PvPers duke it out with others of similar motivation and skill.
All great ideas. BUT these are extremely hard and time consuming to implement from a programming perspective. Simpler solutions are disabling multique or queueing as a raid.
Not that anyone running the server cares that their system is 100% broken