I would like to think that the story content for this patch was short because they wanted to get Dragons and the dark wizard guys out of the way so they can finish up with a ton of content for the ending of the Ul'dah arc.
It makes sense as well if they did it to finish the arc's separately. That last two major patches (2.4 and first part of 2.5) focused on Ishgard for the buildup to heavensward as well as finishing up the Ul'dah questline. It makes sense they would segment these seperately so they then only need to focus on finishing one arc at a time. With Dragons mostly out of the way and ascians out as well, its mostly just going to be about Ul'dah stuff or finishing that up at least.
It makes sense as well if they did it to finish the arc's separately. That last two major patches (2.4 and first part of 2.5) focused on Ishgard for the buildup to heavensward as well as finishing up the Ul'dah questline. It makes sense they would segment these seperately so they then only need to focus on finishing one arc at a time. With Dragons mostly out of the way and ascians out as well, its mostly just going to be about Ul'dah stuff or finishing that up at least.