Just an idea - sort them by days played.
Would be good to balance them out - the people who stopped playing and returned would get matched with people with similar play time. It would also make shards more competitive, erasing the people who hit lvl 20 and stopped playing, grouping them into an 'afk' shard. This system could refresh every month with season rewards, which would also stop easy discord servers allowing people easy 1st. Definitely controversial, but I feel it would freshen things up.