Felyndiira

Battalion Vantage is fun. Vantage itself is a bit underrated as a skill, but it's true that you can't just slap it onto someone randomly and expect it todo things. The Merchant Mercenaries have a use, though, due to their poison gambit having a massive hitbox. All gambits inflict desperation, and your access to huge AoE gambits are limited when you get them, so they are definitely helpful.

I disagree with Wt -3 being bad late-game. If you can use upgraded irons before the skill without penalty, you can now use upgraded silvers without penalty. That's basically another +6 Mt on a skill, except unlike Death Blow it also works on enemy phase. Plus, for axe units, getting Armor C lets them cert into Fortress Knight at a 43% chance. You don't want the actual class, but a free "bump DEF up to 17" is never unwelcome. For Ingrid, I feel that going Wyvern Rider at 20-30 benefits her too much to ignore. She should have the flying ranks for it, so she only really needs a C in axes for a 43% chance to cert into the class. The class gives her an effective +4 permanent STR assuming she's not already strength blessed due to minimum stats. Going Wyvern Rider also gives her an effective +11 to her attack power for level 20-29 (+3 from min stats, +3 from class changing, +5 from axefaire), which lets her kill much easier at this level range. Plus, leveling axes a bit lets you class into Brigand early on to learn Death Blow. It's a lot of skills, sure, but Death Blow helps with her strength problems a ton. Obviously don't do it for LTC or challenges, but it's very helpful for normal play. I actually find it hard to stomach Ingrid's low damage without it.

Think of Fire Emblem as storing a string of pre-generated RNG numbers. Every time the game needs to roll RNG or something, it takes the next number from this set and rolls them. Whether Byleth attacks from melee or range doesn't change this. The game will roll for hit and crit for you, then hit and crit for his counter either way. By "doing something else", the others mean have another unit attack a different target first, or do anything else that uses up some RNG numbers before you try again. Also, it takes tremendous RNG screw for Lysithea to not one-shot him with spikes. Is she underleveled, not promoted to warlock/bishop, or does she not have Fiendish Blow? Base 17 magic from warlock + 3 class bonus + 6 Fiendish Blow + 5 Batallion + 39 Dark Spikes super effective might is a total might of 70, which should rip through his resistance pretty easily. And that's minimum stats for warlock.