Just announced that it runs 8th August to 19th August.
There are two daily quests offered with the Orsinium DLC.
The first daily quest involves killing a delve boss and collecting some items along the way. This daily quest can easily be completed solo. This quest is picked up in Morkul Stronghold which is along the central coastline.
The second daily quest also involves collecting some items in various locations in Wrothgar and killing one of the world (skull and crossbones) bosses on the map. This daily cannot be completed solo by players such as myself (still working on getting gud ). This daily is found in Skalar's Hostel which is located in the northern countryside outskirts of the city of Orsinium.
Both quests award a box
No word on how many feathers if you are collecting for the Indrex.
Possibly 1 from the world boss and 1 from the delve each day.
You will only be offered one WB and one delve quest from the NPC's. However, you can do all of the quests if shared by others. Note: some delve quests will only be offered or shared if you have completed the applicable delve quest. There are 12 dailies in total.