I was definitely, 100% not expecting her to die here. But yeah, I can see how it might feel cheap to have a love interest thrown in and killed in quick succession to avoid having to deal with it in-story. On the other hand the arc works well as a standalone action story. It fullfills the clichés if you're going for the revenge style of ending (and note that FMP is very much a collection of action movie clichés. And that's a good thing btw. It makes it fun).
I'll agree with others on the storyboard front btw. The pacing was spot on and scene after scene just felt right. It never felt rushed or drawn out and I barely even noticed the time go by. I'm also not 100% on board with the usage of the insert song, I also felt like it didn't really fit at that time and I think it's the song itself. It's just not the kind of sound I was expecting there. But, to be fair, I'm not a big fan of the songs this season anyway (including OP/ED). They feel very different from the previous seasons music direction, too "modern" maybe.
Overall those are minor complaints. I didn't even pay much attention to the lack of quality in the animation which just goes to show that it was competent enough not to distract and that the story has me hooked. 9/10 (even if I wanted to vote 1/10 just for Nami's death
)