I think part of their issue is having to slow down the train of the main story, or at least find a balance between the pace of the story and the age of some of the young actors.

 

They've blown through the comic source storyline the last few seasons and are quickly approaching the "end of the line..."

 

Soon it will be where GoT is, where the new source material will be struggling to keep up with the TV programming (with TV possibly delayed by it as well.)

 

I suppose though, with as many original characters on the show, they do have the option of taking a spinoff route and following non-comic characters to delay covering the main story.  That's actually a very interesting concept (like the new Star Wars episodes, throw in the side movies while the main story is still in place at a slower pace.)

---