Yesterday i've completed my first LH insane game as 'undepowered' summoner. I'll focus only on major things

1. AI doesnt know how to play this game in tactical battles. Battle of wesnoth and unity of command are best example that good AI playing on a small hex map can be done even by a small team. Both are great games precisely because AI is better than average player ! AI buffs to stats / production rate can make game difficult but it does not make it fun
   • Units have to know who to attack. Atm they just attack unit that is blocking their movement
   • Archers have to focus on targets they can actually dmg. My mounted wraiths with 3 dodge traits, lucky racial and evade spell are not something you want shoot at when there is a plenty of easy targets around like for example air elemental. Sure wraiths can have less HP but effectively they are 10x more harder to kill than 100 hp air elemental
   • I learned to maximize swarm bonus. AI did not.
   • 2 spiders vs 4 or more units is a disaster they chain cast their abilities from start to end even when it is by far the worst thing they could possibly do. Remove spells that are not AI friendly. They do more harm than good. If you cant evaluate spell usefulness or there is no metric that would allow you to compare spell outcome with other spells / skills just scrap it.
2. I really like that summoner can actually focus on summoning. Fantastic creatures with all their abilities (ligtbringer tank, wisps healer, air elemental great support spells and good dmg etc) are in my opinion much more interesting than normal troops. There is a huge difference between lightbringer and for example fire elemental. Impossible fight can out of sudden become easy if you use all skills you have to maximum. Normal troops do not have meaningful skills so its just a matter of dmg, mobility and passive defence. Racial abilities and weapon specials are small step in right direction. Every time you need inspiration just launch master of magic. MoM paladins, hammerhands, dark elf warlocs are normal troops but they are totally different and can be super effective or super ineffective depending on who you fight. Ofc first you need to solve 1) before you introduce more diversity to tactical battles.
3. All units should scale with level. Goblins lv10 doesnt have to be 10x stronger than goblin lv1 but you should notice you are fighting elite unit. Air elemental or wisps are good example of scaling with level. Lightbringer doesnt scale at all.  

If you fix 1) and do absolutely nothing else at all it still will be a great game If you add 100 new features and leave AI as it is it will never be agreat game.

PS. My scored 18.5k points