Regarding the exp traits:
I agree, they feel almost mandatory. At least make them unlock some nifty abilities

Regarding Summoner: 

Only played 1 game of LH so far, as pariden focusing on summons. Loved what you have done to it. Really felt like a mid/earlygame powerhouse, and i could feel my time ticking as lategame arrived, and my summons became relatively weaker. 

Lots of fun summons, but i did miss an active thing the that the summoner does in combat. Basically i always just passed Porcupine's turn in combat. Adding something like a "rebuild elemental" (heal that only can target elementals) or "chain elemental" (imprison that only can target elementals) would lead to a more active summoner. I assume its possible to have a skillpoint give +1 to summons AND a (not op) spell?

 Regarding Commander 

I did still find the new governor skills still rather "boring", the +100 instant research felt like it arrived way to late. (Netting 100rp instant when making 40 pr turn.. not too good.)
Maybe move it to an earlier lvl? Sacrificing the combat power of an early hero should reap a pretty good reward, especially now that they arrive so rarely?
(lower combat ability due to picking commander slows fame generation, maybe commanders could generate fame?  
Dont be afraid to make them quirky, like if you focus on the research skills , then maybe u can unlock a "grenade" skill with 50% chance of hitting self. Or a 3 (combat)turn casting time spell that does a random effect (summons a shambling golem? Mud bomb , hero explodes?,  just random stuff).

Also, would it work to make some of unrest modifiers of the commanders global? Hero's should be out there, lvling:P

Regarding Warrior
The +attack skills are good, but not too exciting=/ Adding some situational skills would be fun. (maybe a "hit and move back 2 tiles" or the previously suggested Decimate

Hope my feedback can be of assistance

I agree wholeheartedly with this ^   I'm sic n tired of static tech trees they need to find a way to randomize them without making them overpowered in what sequence they come in.

After playing for a few hours i think that the xp talent should be removed and automatically applied so characters level up faster. I am finding the melee characters are generally below par in combat to the point of the game you are up to. Mage class characters seem fine to me.

The generic +1 level traits are boring.  In vanilla FE I chose those only if the Random didn't give me something more interesting.

As is the level trees are 1. too linear & 2. too vanilla.

Solutions i've been thinking about (all already on this thread as I'm posting late):

1. Give more than once choice per level up.  Given, say, two choices per level-up, you could pick one "boring" bump in a tree and something else more interesting on the same level-up.

2. Break the trees into smaller bushes.  Dragon Age II had an OK system for this kind of thing.  I would really like to see smaill mini-trees for each weapon including staves.

3. Combine the vanilla stuff with something more interesting.  -1 spellcasting time and a new spell.  Bonus with swords and a new maneuver.  I've been spoiled by what DND 4.0 did to warriors giving them lots of interesting in combat options.

Some combination of #2 & #3 would be ideal IMHO. 

I think the boring trait lines are the problem and not the static traits. If you have many useful options in every game the trait selection is your DECISION without relying on a random number generator.

If the trait lines would be removed like suggested here: https://forums.elementalgame.com/441857 it would be perhaps possible to include a few random traits in every path to make everyone happy.

I can see the point of those wanting random skills, however that is definitely a subjective matter.  I personally like being able to pick where I want to go.  What needs to happen (now this is just my opinion of course) is that we have so many cool things in each tree that it makes "builds" of different kinds (within each class) all very viable.  Like Wizard1200 said the more interesting and "cool" options available the more enjoyable and "strategic" your choices become.

However, if you are, and never will be, a fan of skill trees then only a random system would likely satisfy.  Maybe there is a really intelligent way to compromise the two systems for both styles of players.

I see your point and I think it has potential. For me at least, one of my favorite things in FE was 2 heroes of the same class were rarely the same even if being built with the same goal in mind due to the randomness. I don't mind being locked into a general set of traits due to class selection but the static builds through the trees are very dull. With the current tree I rarely feel like there's a cost/value issue. There's no longer a feeling after a level where I go "Ugh which of these awesome skills should I pick this level." Feels bland and straight forward.

Specially for warrior type heroes. It seems logical for generals and wizards to do only 30 damag in melee combat even if they are high level, but a high level hero that can't fight against six trained units is no hero at all.

I am afraid that the overpower ability might be too overpowered (as the name says ). Perhaps a weakened version of overpower could be a trait that could be chosen by a warrior, or if you are allowing the warrior to pick overpower, place it at the end of a long branch. 

Maybe another solution (even complementary) could be (I am just making it up as I write) to give every champion attack and defend increase bonuses each level. For example, let's say that Defender has +1 attack each 3 levels and +1 defense each level, Warrior has +1 attack each levels and +1 defense each 2 levels, Commander has +1 attack each level and +1 defense each 3 levels and so on. The actual numbers would have to be worked. So your level 20 warrior would do a lot of damage to a level 1 hero, but not so much damage against a level 10 warrior and even less against a level 10 defender.

Perhaps the overpower ability of hammers, mauls, ... could start at 50 % damage and could be upgraded like the damage of the counterattack ability. Giving those weapons overpower would make them interesting, but not too powerful, because they have a huge initiative penalty.

Passive attack and defense bonuses would work, too, but i think it is more fun to select a trait or a weapon.

Maybe each hero should come with unique abilities that only they posses.  Having 2 or 3 "cool" skills that are unique and that once the level up trees are improved allow for different combinations with those special skills creating unique heroes that can be leveled up differently each game due to the different styles and combinations.

I really hate exp enhancing traits/perks/feats in general. They are either useless noob traps or mandatory free power that makes early leveling boring. Would hope to see them completely removed (except as starting factions traits and such).