Neither capping nor CRZ ensure balance in numbers unless the number of players who'd like to Ashran is vastly larger than the number of players who can do so because of the cap (won't happen because Ashran is an all-day event). Equal numbers have to be enforced.
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Unless you face a semi-premade of 40. Happened all the time on some realms. :-) But wasn't very fun. :-/