Oooooh that's a fancy Est! I have built a Cherche similarly to that, one of the first units I ever built out lol. I gave mine drag back because hit and run was even more rare at the time (might've been just after when Clair was added to the 4* pool, I think?), and I didn't have any Kleins for death blow 3, and the difference between death blow 2 and attack+3 (her default) was only 1 point, so I kept attack+3 lol. She originally had fortify fliers, from my one and only Caeda at the time (I've summoned more since), but I have since switched to goad because running a team with 4x goad fliers is hilariously strong (+12 atk / spd with a good formation is hilarious), and is immune to panic ploy. The original Cherche was a lucky summon from the fliers voting gauntlet, so her IVs are sub-optimal, but she still cleans house as she is.
Not sure if you have the fodder for it, but have you thought about trying def ploy on her? I remember there being a meme in other communities because she was given a very high spot on the tier list because of how many units should could destroy with it. Sadly, def ploy is only available from Summer Gaius, who has long since been off the regular rotation, so I can understand if you don't have him.
And yeah, I've liked how the defiant skills have worked on my healers. It isn't the best choice, that'd likely be HP+5, or the relevant stat up +3 (usually spd+3 or atk+3), but it's funny when my defiant def Azama gets pinged to low percents by the AI, and then stops taking damage from them lmao, and can just tank everything they throw at him thanks to defiant def. I mostly use healers in stamina modes, or in arena assault to keep my mainline units healthy, especially if a map has a lot of strong units in a single color, so I can use the same unit with weapon triangle advantage to take them out without worrying about the unit getting chipped down and KO'd.
Not the original builder, but I can see a thought process for this, at least from my own personal perspective (if only I had a Hinoka myself....
). I would say that Est benefits from hone fliers, but doesn't straight up require it. If Est is anything like Cherche, that brave lance should decimate most of the units as-is lol. The units that straight up require hone fliers are the tome fliers, so either spring Camilla or summer Corrin. Est would make a great team support for one of those two. That Est is built to player phase like a pro lol.