I am not sure Little Boy Lost was asking about the hierarchy among the diaconate. (though it is an interesting topic) Rather I think he was asking about, specifically, monastic deacons or hierodeacons.
I am not sure how many hierodeacons there are in the contemporary Orthodox and Eastern Catholic Churches. I would guess that most large monasteries have at least one hierodeacon to serve the community.
Do their numbers fall behind hieromonks and unordained brothers?
I would say that the majority of Eastern Orthodox monks (and I would guess it would be the same within traditional Eastern Catholic monasticism (not ones based on a western model) is that the unordained monks outnumber the ordained monks by a wide margin. Within Orthodoxy an abbot doesn't necessarily have to be ordained a priest.
The monasteries I have visited (both Greek Catholic and Orthodox) have all had at least one hierodeacon.