SolrCloud collection CREATE will put multiple master shards on a single node (and no shards on some)

This is best described by a photo of my SolrCloud admin: http://i.imgur.com/hW4xnxy.png

I have a 4 node cluster, with shard count of 2 and replication factor of 2.

After running something like,

http://localhost:8983/solr/admin/collections?action=CREATE&name=15724&numShards=2&replicationFactor=2

The shards seem to be completely randomly placed, which is fine, but some nodes receive more of the share than others (some even receiving none).

For example, 15724 has given node "backfill-1d" 2 "parts", 15724_shard1_replica2 and 15724_shard2_replica1 but has given "backfill-2d" nothing at all.

This creates unnecessary load on some nodes, no? Is this something I am supposed to handle myself (I looked, but don't see how).