Had some problems with mod so i tried to change some files back to original settings, and run in this mistakes in skills.lua file.
Also i found tihs in skills.txt for learning skill it says :
learning {
pos=0,2
deps=trophy
pic=skillicon2_05_
script=skill_learning
name=skill_learning_caption
hint_header=skill_learning
hint_text=skill_learning_hint
levels {
1 { pars=+10%,+1,+5% }
2 { pars=+15%,+2,+7% }
3 { pars=+20%,+3,+10% }
+10/15/20% are bonus exp from battles it`s OK, +1/2/3 is bonus to intelect and it`s OK, but WTF is +5/7/10% bonus for ???? It`s not explained anywhere.
They rly left bunch of crap in this game from original The Legend. No wonder editor crash like crazy, poor thing doesn`t know what`s happening :-(

Those skills that lower the leadership for archers didn't even exist in KB:TL (unless it refers to an item) and they shouldn't appear in the editor,weird thing they do. Ejem also this is probably a bug from the original Legendary Units mod, but the Ice Ogre can use the ogre rage ability unlimited times (in the same turn) thus giving him a lot of attack and ap and no matter what if he uses any ability his turn won't end (the hunger skill is broken I suppose giving you the chance to use all the abilities in one turn).

@Pip_boy Thx for info about iceogres, havent tried so far but good to know in fights against them :-) Some suggestions about fixing this ppl ?
I found similar problem with king harl unit. His abilities need to be changed a bit to work :
encouragement {
script_attack=kingharl_encouragement -delete kingharl, and type special instead

second_wind {
script_attack=kingharl_second_wind -same, delete kingharl and type special.
It`s a bit weird with them : cost 1200 (12000 should be right) , only 1300 lds but make 120-160 physical dmg. To high dmg for so low lds, 80-120 should be enough(same lower their dmg vs dragons 160-240 instead 240-320). And add them in morale.txt file to give +1moral to humans, just add them next to griffin2 in unit2race strings.
And new iceball is also to strong : 10gold cost(way too low, 400 better), physical res to high, 18-24 dmg for 3rd lvl unit to high also even half of that is to much, spikes also too high dmg for low lvl unit.

Found big miss in exp_system_cfg.txt need to add all new units to base string: harl, iceball, iceogre, maelstorm, legendaryphoenix, titan, dictator, sinister, fire/glas/venskeleton, celestial_snake, griffin_spirit, evil book. Place them in their categories :
light shooter - add fire/venskeleton, satyr(replace him from shooter class2lvl unit belong here)

shooter - gorguana_spirit (replace from heavy shooter 3rd lvl unit)

heavy shooter - what unit is spiritist ?

light trooper - glaskeleton, replace pirate_ghost to trooper class(3 lvl unit), add bear from trooper class(2nd lvl unit)

trooper - add dryad,griffin_spirit, bat, evil book , remove bear, unicorn and unicorn2 (4th lvl unit goes to elite trooper)

elite trooper - add orc_hunter,shaman,shaman_blood,bat2, snake_celestial , remove witch_hunter(move him to trooper 3rd lvl unit) undead_brontor move to heavy shooter class(no idea why but brontor is there so i guess it`s ok)

healer - add legendaryphoenix

battle mage - add sinister, gorguana_elder, beholder2, mistik, gorgon, evilbook

suporter - add sinister, legendaryphoenix, iceogre

highlvl - add harl, maelstorm, legendaryphoenix, titan, iceogre, dictator, sinister.

It didn't mentioned them to be shooter. It's a mage.

About other options:
the Exp.system is build in case to make creatures with summon abilities more profit in summoning, not very effective heavy warriors (like bears) to have more HP (so the're in heavy trooper group). Different groups provides different bonuses. I've spent a lot of time to craft this system and to balance it. So be cautious.
Some creatures added into several groups. It's made to give more variety and to allow them to get more randomized bonuses.

Ok i thought units were placed in classes by lvl. But in this adaptation mod RSE i found couple stacks 12k sprites,or some other 1st lvl unit with 45Hp, 9inititative, 5speed so i got into checking what bonuse is at disposal to which unit.
As for satyr i think they need more initiative/res then hp to be able to heal ally before they all die. Hp will only make them more vunerable to burn/poison, and wont protect them from archdemon halfing/lightning ball kill% .

I really like this mod so far. It's extremely hard though! Any tips on unit composition?

Right now I'm running:
Red Dragons
Black Dragons
Legendary Phoenix
Cyclops
Giants

All the units I'm running into now are lethal/invincible. :(

Try using Maelstrom and only Maelstrom for fire, magic and physical attacks. Make sure he has 95% resistivity for the damage type the enemy units do. For poison damage use titans (very good with Maelstrom for physical and magic).
The other thing you must have is the lightning ball maxed out for yr. pet dragon.
Using this i cleared everything including Montero, Tekon, and Dersu (including boss fights). I played impossible mage.
Titans are good but i can't resurrect them using Ancient Phoenix, or Legendary Phoenix.
It helps having double cast for mage. At the later fights when 5k, 6k units are common you will take aroung 200 damage per hit even with 95% resistance, you will need to heal a lot (another thing about Titans you can't heal them - using spell 1 mana from spell book).
Forget about mana and rage items, put as many leadership reduction items on the hero. I got Mealstrom at 2450 leadership cost. Make sure you level yr. units to lvl 10 it will be a little to late after you clear out Verona (to many units to do solo - in order to lvl fast).

@Lantisu10 Well you ask for advice but havent said what hero class you play. You could drop giants, and if there is any dragon bonus item in game go voice of dragon 3rd lvl green/red/black dragon, legendary phoenix and harl (alternative is bone dragon). I know he`ll get -moral from dragons, but he can second wind any unit and have 9 basic initiative so you almost every battle play first (spell/pet dragon).
If no dragon bonus then you could go all melle mash like shrek build but with mealstoms.
@yujy Maelstorms are good for mage, but great for warrior(counterstrike), double cast is nice for buff spells, but you just wont make enough dmg to semi solo maelstorm he need attack bonus from might skill tree. And how did you get them to 2450lds ? Only ancient ring lower their requirement -10% , from 3500 basic it`s not what you say.

Quite simple actually. I got commander's cape -10% requirement and knight set -20% requirements. I total -30% which adds up to -1050 leadership per unit. I actually got 2 commanders cape but i didn't use both (i could, but i used robe of the mages)
I didn't use them as damage troop, i used them as rage generators and because they have much HP and great survivability, easy to heal through healing spell, easy to resurrect with Ancient Phoenix . I used ball of lightning for most of the damage. I also used Legendary Phoenix and Titans with Malestrom against magical damage units (like upgrading items, getting the stone from dragon Stark/white dragon, i believe it was the sorrow stone)

At lvl42 leadership 20k+, 8 Maelstrom all skills researched (warrior, paladin, mage) they could handle anything. I did 10k damage on critical. They would get 120-130 attack and 200 defense. I also used the spell which adds fire damage (i forgot the name, maybe hell's breath) which would give me a damage of 200-250 per unit (without considering the difference between my attack and his defense and other bonuses). This kind of tactic would be impossible with warrior (no double casting)

OK as i said double cast is neat skill, but if you played warrior before you`ll know that at 42lvl you have 40+Klds, and can bring 17+maelstorm with much higher basic att/def making 30K crit hits and with counterstrike skill, making him retaliate 4 times/round and this is also tactic impossible for mage. Every hero class have it`s perks, that`s why i asked Lantisu10 what class he play, and what item`s he have at disposal before i suggested some combinations to him.
And i just now figured out imba info for maelstorms lds, as you said 2 commander cloak upgraded makes -30% lds, and if you find ancient ring would get them to 2100lds/unit pretty sick :-)