1. Farm on your main and switch to the alt when you spend all your Blood Shards.
2. Farm Death's Breath's on your main and upgrade rares in the Cube on your alt to get the desired items.
3. Join a Public T13(?) game (on your main), see if there's a player with the desired class in the group and ask him/her to drop some leggies/set pieces for you.
Worked like a charm for 2 other classes for me.