Drop rates for motifs are intentionally low. Typically 1 in 10 odds at best.
The best way to get these is to organize a guild event to do many of these dailies in a group. Have one person in your group pick up the quest and share it. Then, go out and complete it and turn it in. Then, have the next person pick up the quest and share it... then repeat until you run out of new dailies from your group. I used to run events like this back when I was collecting motifs, and if you can't do it in a guild, you can sometimes find people in zone to work with too. Be a fun and entertaining host too, if you can.