Wisdom is obviously the top of the list, since it decides how fast everything else grows, affects a lot of secondary skills that you really don’t want to mess up on, covers a lot of loot notices/stat checks, and affects the speed and payout for several Operations (like Scouting).
Agility takes the silver metal, since more AP means more of everything; it doesn’t matter if your sniper has flawless aim if they don’t have the AP to get LOS on a target and fire. Stealth is also just as powerful as it always was for picking off lone enemies and setting up initial combat positions.
Dexterity takes a respectable third, since it is your main accuracy stat, affects several important secondary skills, and is occasionally needed for direct checks in the game. It also affects the chance of an instakill while stealthed.
Health is fourth. While it does decide your HP, you’ll ideally never get hit enough for it to matter. Based on what I’ve seen, it also affects how long it takes for a merc to get tired; low Health mercs seem to get burnt out noticeably faster than those up in the 80s and above.
Strength is last. It only really matters if you hate yourself and are putting someone on a suicidal melee/throwing weapons path. The default range on throwable explosives is already pretty good without Strength modifiers, and you’ll never want to use a crowbar to open a loot container when lockpicks exist. It does come up as a stat check in a couple of places, though.
Marksmanship at the top, obviously. Dexterity may contribute to general accuracy, but you need this to hit with almost anything that isn’t melee. Unless you are a patient stealth god, then you’re going to get into fights at some point and will need to hit targets.
Explosives in second. Crafting for both specialized ammo and explosives is handled by this stat instead of Mechanical, it affects accuracy on thrown explosives, and helps defuse (or steal) enemy explosives. It can also replace lockpicking doors but not loot crates; a hole in the wall is a valid entry point. Lastly, one block of explosives taking out 4 enemies is pretty efficient.
Mechanical in third. Several important checks require this skill, like defusing traps, modding guns, and opening those juicy containers without shattering everything inside. It’s also used in a few specialized Operations. Outside of the handful of “you need it now” moments, though, it’s pretty much optional; you can live without that one loot container, and why mod weapons when better ones might replace them entirely after a couple more sectors?
Medical sits in fourth, though it might feel like last if you play perfectly and never get hit. If you truly never get hit by anything other than grazing blows, then anyone with at least 25 points can reliably handle the scratch patching after combat.
Leadership is last. You only really need one person with high Leadership, and then they handle everything that involves it. Two people with high Leadership don’t really speed up militia training all that much, and you obviously can’t have two people negotiate something down. Personal morale also seems to not exist in this game and instead relies on guaranteed “all-or-nothing” personal interactions and the group morale AP boost from special kill situations during combat.