Desperate measures - take your level 3 Titaness to the Divide and let her join the public event when it happens there. Once is is done at gold level, then go to the postmaster, pick up the thing you get (shard, energy etc) take it to your vault, drop it in and then kill her. Then create another character, run her through the start up sections - take her to the divide public events, get the postmaster package, drop it off in vault and repeat endlessly. This method usually gets shards more than anything else - I did it for 18 shards once, but its rather unpleasant and if nobody is in the divide to help you then no gold event. But if you are fast then you can work it so to get three Divide visits every hour (potentially 3 shards an hour). Alternatively just get in to the habit of taking all three characters to a public event EVERY day and once you have a gold reward then collect the postmaster package. Over 3 characters thats 21 packages a week and probably 10-15 shards depending on RNG. Plus a coin or two and ascendant energies. And buy legendary gear to break down for shards.