Let's not get into a debate about whether or not the mourning someone's death gets, should be relative to the amount of suffering or joy they caused in life. What I'd say matters is that Ysayle, for all that she spent a lot of 3.0 with us, received a dying scene that was not only frustrating, but also felt unnecessary. Because it all could've been avoided if we were smart enough to avoid doing all the Garleans' and Thordan's work for them.
Similarly, this is what I didn't like about the Scions' and Haurchefant's sacrifices, in 2.5 and 3.0 respectively. Both of those could've been feasibly avoided if the WoL did anything besides standing around looking pretty in cutscenes. I'm pretty sure Zephirin's spear wouldn't even have hit us if we'd just kept running, or stopped running. Killing off your characters feels rather empty if it requires your main character, who is constantly being talked up as a prodigy that can prevent such deaths from being necessary, to be a complete idiot and forget all their skills.
Here's the thing: I was already fully aware of how dangerous a place Eorzea is. It's written into every line of almost every quest, FATE, and even in some NPC interactions. Simply watching little kids learning how to fight with lethal weapons is a stark reminder of that. I didn't need a Tale to write in a character for the sole purpose of killing her off, in order to express that. From the detail that is shown of Alisaie's reaction to it, I'm fairly certain the purpose of the whole character death was also to add pathos to the story. Does Emery do anything for Alisaie in life, that another situation or character couldn't do just as easily?
From the whole story, Emery serves more of a purpose in Alisaie's character development, when she's dead, than she does when she's alive. Which shows that the main purpose of the character was to die, and I don't like it when writers can't do anything with their characters except kill them off.
Lastly, it is entirely possible to write a short story that has depth and compelling character interaction and development. I've seen several other Tales do it just fine.