Since survivors started to realize how unfair it is if you are versed against a player from the different side of the rank spectrum, maybe we can talk about a rank lock system.
Its common among all other competitive games I know, so why not do the same in DBD?
The killer rank could be used as base niveau and only survivors 3 ranks below and above would be considered for matchmaking. Of course this would mean in return that you could only play SWF with players that dont have a higher rank difference than 6.
of course those numbers are just a suggestion by me, maybe they should be even stricter and be reduced to 2?