tbh, i do find most of stannis' arc a bit dull, but in the most recent episode his arc was quite entertaining. the burning and the dynamic between his wife, priestess and daughter was bizarre and fascinating. like peeking into a secretive and self-possessed royal family. I can feel the old blood's pride in Stannis, despite having to live in that gloomy, strange and misshapen form of 'glory'
Bran, yeah, his plotline is slow moving and full with nothing but trudging here and there. But I consider his arc to be the slow burner whilst the current primary story is blossoming in pomp and fanfare. So, I find that I am accepting the slower pace and duller happenings in his arc, because I am expecting that his stuff is more aligned to 'future' things. Sometimes I think he's just told to remind audience that hey, stuffs are being set up here... for later.
Also, whoa, the actor that played Bran grew a fair bit! : O