We get a level 100 talent for an ability, that mostly is for PvP. In previous expansions, especialy the first 2, a new expansion meant a whole new set of abilities and rotation. We are talking core abilities like Dual Wield for enhancement shaman in TBC, Maelstorm Weapon stacking in WotLK etc... A whole new rotation meant the game felt "new" and it was fun to look up optimal rotations etc.
With 1 new ability, and a few "upgrades" on core abilities, your rotation will barely change. You have probably already mastered your rotation in the current expansion.
TL;DR: Will raiding get boring quickly when there is "no new rotation"? Can fun tactics alone carry the amount of fun you will have?