Haurchefant's a big deal because he saved the WoL's life. It was literally a personal sacrifice in a very personal way. Remember that Zephirin's lance of light was intended for us, just after Ascian cutscenes where they shared with Thordan how to kill Echo blessed individuals. He was life changing in the fact that he's the reason the WoL is still alive. Indirectly the savior of the entire universe, yo.
As for y'all saying he was barely in the game... He enters the story right after The Waking Sands massacre, and he's the only Ishgardian friendly towards the WoL. You stop an execution together. He gives you an in with the other houses so you can find Cid's airship. Later he's involved with the Shiva questline and response to heretics. Introduction of Aymeric. Then he takes the WoL, Alphinaud, and Tataru in after the Blood Banquet. Then he provides a means for them to enter Ishgard. Then you save his little brother Emmanellain with him, and then he's absent from your travels until just before The Vault as he's still duty bound to lead Camp Dragonhead. But he re-enters on your side without question, and assaults a member of the Heaven's Ward in broad daylight in the city center. He's unquestionably loyal and cool, and I honestly don't understand folks who are like, "Who's this elf bozo?" It's like y'all aren't even playing the same game at times.

Ysayle's death kind of comes out of left field, and I still wonder to this day why the clever Iceheart didn't sneak attack the dreadnaught. You know, the woman clever enough to slip past the guards and disable the outermost layer of Ishgard's forcefields? There was really no reason for her to approach it head on, other than to up the drama.

Papalymo's death stunk in a lot of ways. It just reeked of, "Hey let's get rid of this character we don't have a place for in Stormblood, even though we should." No build up for it, and no real pay off since it happened in 3.5 and then by 3.55 Shinryu broke out and we had to sic Omega on it anyway.