The Good Parts

• The Blue Dragonflight questline. Call backs all around, and it wasn't simply nostalgia-bait.
• The Old Hatreds questline. Baine does something. He gets an arc, then completes it.
• Thaldraszus time-travelling. Zingers range from being sent back to your starting zone, and hearing so much Old God whispers that you understand how people went crazy.

The Bad Parts

• Ysera came back, did nothing, and then promptly left.
• Alex (and Vyranoth) were undercooked. Neither were given enough spotlight to have an engaging story.
  
• Sarkareth and the Sundered Flame were not properly introduced to players who didn't play Dracthyr. And Dracthyr only fared a little bit better.

The Mixed Bag

• Tyr. Present since the launch of Dragonflight, I don't know if anyone expected that it would take until the literal end to finish it. Had some good parts, but probably overstayed its time.
• Scalecommander Emberthal. As the main Dracthyr, we get to see her have her own arc (which was good), but it meant the actual Horde/Alliance racial leaders had zero presence (which was bad).