Well, at least she got cool looks for the cinematicNot for the Night Warrior concept, but I was talking about a waste of Tyrande's story.
The Night Warrior is fine as a piece of world-building lore for the series. Showing Tyrande become that form opens up an aspect of the world we haven't seen before.
But in terms of her character arc, it was utterly pointless outside of being able to kill Nathanos. The writers had her fail at every turn to kill Sylvanas, and it was all intentional since the writers had no intention of Sylvanas dying at her hands in the first place. Kinda like how Maiev was written into Warcraft 3 TFT purely as a means to give Illidan some depth and exposition. Even though we get to play as Maiev, her purpose in the story is just to support the grander narrative focus which is meant to be about Illidan vs Arthas. Tyrande is being used the same way, to give expository depth to Sylvanas.
If the writers weren't so adamant at reusing characters instead of creating new ones for the purpose, we wouldn't have all this circular bullshit of having named characters always be propped up and downplayed in power with no consistency to what they're actually capable of.
Kinda like I pointed out earlier with Anduin being High King of the Alliance, with powers to make himself invincible with the light or ressurect entire armies, and is surrounded by the most elite guards - Easily kidnapped by a few flying Mawsworn in broad daylight. If they wanted another 'Lich King' character, they could have just created a new one for the purpose instead of using Anduin, but you see the writers consider this 'character building'.