Doing the dailies for each just seems irrelevant after you maxed out their respective skill lines because the only real reason you do the dailies is to level the skill. The rewards are simply not good enough. The only good rewards are the motifs, and they are too rare for something that you can only do once a day. For example, I could do a sacrament that was kind of hard, then go back to the Sanctuary and pick up my reward only to get a green weapon with no effect, which is an item that you could get within seconds by killing an npc in the world lol.

My suggestion is adding new armor sets that are actually good that drop more frequent from these coffers. Sithis is cool and all and I understand ZOS wanted to do something with Blade of Woe, but I'd love to be able to use a DB themed set in endgame PvE. Another good idea would be to add Thieves Guild/Dark Brotherhood themed furnishings to EVERY coffer. I understand the DB has the Shadowy Supplier, but he only gives DB themed stuff and it's too rare. So if someone truly wanted a Thieves Guild/Dark Brotherhood home, they would need to farm those dailies to get those items.

Basically, I just feel that once you complete their skill lines, there is really no reason to bother doing the dailies. At least not for the rng motifs that you can't exactly grind/farm for.