What is your expectation when you say "what are drop rates based on"? That a character that does the average number of dailies per day will have all motifs at the end of it? All Worm Cult motifs?
We do dailies, we get crafting mats, furnishings and motifs. People who do more of them will get more. There is a time constraints as well. Even if you have 12 characters, you can't possibly do 50 dailies on each of them.