Try farming them in normal mode. As these drops are festival related, they are exempt from loot scaling - and they have just as much chance to drop from weak monsters as they do from strong monsters. Plus weaker monsters die a lot faster, so you should see things drop faster.
Pick an easy area where you can farm solo. As stated, you will get the non-scalable loot dropping regularly. In addition to CC Shards you can farm 'collectable' drops from specific mobs.
