Bronn, Brienne, and the Hound are all still alive in the books. What they are NOT, is in the middle of any central story going on. Hound is in a monastery, took his whole piece off the game board. Bronn married a Lord's daughter, then kicked out his new parents in law, so now he's got a castle and could give two fucks about anything. Brienne almost died until she said something to Lady Stoneheart and I guess she's off to get Jaime for her. D&D are such TV creatures, they couldn't bear to deny fans their favorites. If it was up to them Robb and Cat would still be alive in Frey's dungeon, until their final rescue by Faceless Arya.