Collection of tips from various sources here.
General Tips
- Exp growth is greatly reduced. Always try to have Byleth adjacent to the unit getting exp, particularly for the killing blow.
- Give a bow to every physical fighter. Some guides recommend giving a bow to every person, period, but I think I can trade them around if my mages really need them.
- Healing exp is not nerfed, unlike other exp. Get as many people as possible Faith D for heal. Mercedes, Ashe, Sylvain and Ingrid all get Physic, so C rank for some of them might be a good idea.
- Every physical fighter will master Brigand, and then Archer if they have the time. Every mage will master Fiendish Blow. No other beginner class is worth the seals or time for most characters, with a couple of exceptions.
- Going on that vein, every character should get to at least D+ in axes and then save scum until they pass their certification for brigand, as well as D+ for bows if I have the time and money.
On Grinding
It is definitely possible to grind in Maddening--just very difficult. It is also limited. I'm not sure if other routes have this, but in maddening each map is capped at 99 turns.
In essence, grinding in FE3H boils down to having the bad guys whack your highest defense person until all their weapons break on his face. In the meantime, if he needs training he can reciprocate by hitting back with a broken weapon, therefore guaranteeing that you will get weapon and class exp for as long as possible. Problem is, given the 99 turn limit, causing the bad guys to break their weapons eats up about 40-60 turns already. With a unit with sufficiently high defense, however, this can be an incredibly fast way for one, or more, units to train.
I will save scum so that Byleth and/or Dedue get a defense level every level. Then I will give them a silver shield, Duscur heavy soldiers, and have the other be an adjutant to maximize their defense. This is crucial for recruiting other units, as it'll allow my Byleth to quickly train all the physical weapons, authority, as well as riding/flying/heavy armor if they're in the appropriate classes. Other units will try to train as much as possible on enemies that have broken their weapons, so that we can save time on lectures.
The things that Byleth CAN'T grind are Reason and Faith, as well as initially Heavy Armor, Flying, and Riding. With that in mind, it is VERY useful to do the choir activity every time until you hit at least D in faith, and when you are doing faculty training, to train armor, flying, and riding. Once you hit E+ for heavy armor/flying/riding you can save scum while taking certifications and then grind the levels. Just remember to use magic and faith as much as you can every chapter.
The units I want to recruit for Blue Lions include Hilda, Leonie, Petra, and/or Lysithea (what can I say...women in this game are just better imo). Ideally, I want to just train the stats needed to recruit them because I am very afraid of getting screwed with the random recruitment system...but I may not get the luxury for that. For future reference though, they require C in axe, C in lance, C in riding, and C or B in Faith respectively. All these are relatively easy except riding which I'll need to go out of my way for. I want to recruit everyone eventually for their paralogues and also because I don't enjoy killing students.
Lectures and Goals
Each lecture you get up to 5 (or 6?) uses, if you get a perfect (and/or a bad) and praise (or console/criticize) them.
With maybe one or two exceptions, everyone will get Faith D for the free uses of heal. The next thing to focus on will be Axe and Authority, until they get Axe D+, then switch to Bow and Authority till they get Bow D+. Then they move on to skills their main classes will need.
For Felix, authority training isn't as urgent as he is better without a battalion in the early game. He will focus on sword instead.
For Dedue, heavy armor will be an early focus, with the hopes of reclassing him to armor knight ASAP. The hope is that, in conjunction with the heaviest shield I can find, Duscur battalion, and another defensive adjutant, Dedue will be so tanky that he can have enemies break their weapons on his face, allowing the rest of my characters to safely farm.
Reclass everyone except the people not using faith into monk to continue capitalizing on the free exp heal gives.
Chapter Rundown
Chapter 1:
Trade Claude and Edelgard's weapons and vulneraries to Dimitri and/or Byleth. Dimitri and Byleth take all the hits and do all the damage for max exp. Use forests to your advantage.
Try to head north with Claude and Edelgard to draw the enemy soldiers north, hopefully causing Jeralt to steal fewer kills near the end. Jeralt can't kill the boss so if he can only target the boss it's fine.
Chapter 2:
I bring Sylvain, Annette, Mercedes, Dimitri and Byleth. Felix does a lot of damage and I want to try to grind. Given that I had shared a meal with Annette and Mercedes maybe I should have left them home.
The A.I was really fascinating on this one. Advancing north causes all units to jump on you, which is messy at best and impossible at worst. Going west and killing Hilda, Claude and Hanneman causes the black eagles to all aggro and attack you in a way that's awkward to defend against as Hubert is within supporting distance of Ferdinand.
The best way to approach the mission is to go west, kill Claude and Hilda, then go back east to the starting position. Inch your way to the single square that only aggros Ferdinand, kill him with focus fire, then aggro Hanneman and kill him. With just Edelgard and Manuela left, cleanup should be relatively easy.
I trapped Manuela and farmed. Everyone got ok to good levels, except Sylvain who got a whopping +9 level. Trained most to level 4ish, and trained Dimitri's lance to C. Should have given his broken lance to Byleth. She did get some uses, reaching E+.
Aux Battle:
The game forces you to do an aux battle after Chapter 2. The enemy stats are more in line with hard mode than maddening, making it rather easy. Park all the units in trees and heal as necessary.
I gave Dedue the broken lance and got four enemies to attack him until they broke their weapons. Meanwhile the others kill everyone else. I then give Byleth the broken lance and grind.
Almost all characters ended up mastering commoner/noble, which is great. Dedue and Byleth were able to go straight to rank C on both authority and lance, which is amazing. Funnily enough, not a single person got a level up.
I will try to get one broken weapon of each type so she can hit C rank on everything. Given the 99 turn limit, she will be able to hit rank C for two weapons per auxiliary battle if she ever gets her Def high enough.
Following the lectures, the saint's day, and the seminar (which nicely bumps all my half motivations to full motivation), Annette can now use heal. Ashe and Sylvain JUST didn't make it. Arghhhh....I guess we'll have to go into the next match with just ten uses.