But for the other Dragon Ages and Mass effect there were DLC with a lot of roleplay, story, new dialogues, new cutscenes with characters... So why are they making only DLC with just dungeons/new map for DAI? I'm waiting for à true roleplay DLC like Awakening.
That may be coming. I suspect the first one, and possibly this one, were planned for DAI itself, but they put them on the back burner because they didn't have the money and time resources to do them as well before the game released. It just makes sense that they'd finish up stuff that was partly worked out in advance and clear them off the table first. Even though I would dearly like more story, etc. (especially for the dwarves who got almost zip for story and a lot of really sloppy cinematics in DAI,) I'd rather they take the time to get them right, especially since they would start knowing they had to adapt them for different races. The Cullen and Solas romance animations in DAI, for instance, show a lot of incredibly meticulous and loving work by several someones (as well as increasing skill with FB,) and that's time consuming to get right. There were complaints, some in reviews I think, when the game released that you didn't revisit the Deep Roads during DAI (a lot of people who are less attached to story loved the Deep Roads, they just don't talk on this thread.)
I think they've said they know people want more story content, but I'm betting they didn't do more than tossing ideas around until the game released and people began pointing out problems and gaps they overlooked. We don't actually know for certain yet that there aren't some cutscenes or dialogue in Descent - they might be trying to avoid spoilers. And there are cutscenes in JoH. However, if it's just the probable absence of Cullen, well, although there are some things they should have addressed connected to him and obviously he was very popular, he also received a lot more content in and out of the romance than most of the others already. And getting GE back to do the VA could be a problem in itself due to his commitments. I would actually be very surprised to see any significant new content with Cullen, to be honest, though they could surprise me. However something they might do if people campaigned very politely are hugs on demand for all LIs. That would mostly require animation and programming I think (no VA,) and might be able to build on work they already did. 