Maybe you could slightly change the cinematic when you loose the obelisk, so it becomes a "You Loose" cinematic?
Imo it should definitely be more dramatic. They are the main characters, and the love triangle is one of the main plots in the story. Maybe also add more dialog in Tyrande's fight how she loves him and can't kill him for that reason. Making a point that her love killed her. But that's just me and it's your choice.
So Alexstrasza and Nozdormu boss fights were cut out? Too bad
. Time is always limited
. It's still one of the best campaigns out there. If there are no ideas, maybe look at HotS or WoW again for inspiration. If there is no time maybe just make her die in the cutscene when Malfurion consumes the World Tree and destroys the World Tree. Would still be lame for the death of the Dragonqueen, but better than nothing.
One more question. Have you considered renaming Lady Darkscale to Lady Vashj(she survived the Dreadlords)? I mean it's hard to imagine Illidan and the Naga without her.
Also can you give me a small spoiler. Is it planed in the Sentinel story, for Tyrande to have a larger role, possibly be the main protagonist alongside Malfurion? Also I know we won't be fighting allied bosses in the Sentinel story(e.g Tyrande, Cenarius, Velinde), but also not the Sentinel enemy Highborne bosses(e.g Shahraz, Kazzak, Smolderas, Azshara)?