You obviously don't know how this realm works. No matter how much they increase the cap or kick afk, there will always be more people. This realm started with a 5k cap if i remember correctly and has grown to 10k. So even if you increased cap to 15k, people would hear that there's a 15k server and then you would have even more people coming. I think you're forgetting that WoW once had 12 million players in time of Wotlk and that there will never a shortage of players. I think this problem can never be solved.
Limit the amount of logged in accounts on a single IP. No one needs to multibox more than 5 at a time.
I don't mind waiting in queue but when 3 people i am talking to can instantly log in after i have been waiting in queue for 2 hours and still have 2 hours remaining then i think that is completely unfair.
I am not sure if this realm has it but you should have a daily restart before peak times to disconnect any afk accounts.
You blame multiboxers. I wonder what happens if they start doing the same and blame those who don't multibox.
Just like blaming cows for the greenhouse effect.
Queue might reduce a lot after Ragnaros and Deathwing are upgraded. You can consider playing on those realms if queue is that annoying, or accepting the queue if that's best for you. For now, a new realm is out of option.
Anything that negatively impacts performance can't be done, either.