The legendary heroes of this mod are very cool, I like the ideas and like the use of our new customizable demon prince to bring these heroes about. I am mostly talking about the 4 monogod legendary heroes here, as I mostly play Khorne and the other 3 gods are easy enough to check their skill trees on turn 1. So for the other legendary heroes like the shade of Be'lakor and avatar of Ursun I've not yet checked, so for them I don't have any specific changes in mind. This will be lengthy but here we go.

Khorne, first up because I play them the most. The bottom skill line is a bit weird with how it's laid out. I'd instead just leave the normal hero skills there, or cut those skills almost entirely. The bottom line can then be changed to action success chance and cost reduction, public order (now control) and khorne corruption, and xp per turn for army and replenishment. 3 skills with 3 points each, if you want also stick the 3 locus skills down there. Next there's no need to have 2 melee lines, I do understand that you gave the other 3 a lot of stuff too but one at a time. Just keep the one melee line with bloodthirst and deathbringer. Instead of a 2nd melee line from the hero tree do a smaller line with some of the other abilities and several other bonuses. It can start with rage incarnate, then do gorefeast, a skill for melee attack and weapon strength, a skill for hp and melee defense, and then passive ability tempered rage, then do wrath of khorne at the end. The spirit essence of Khorne and Fate of the forged can stay where they are, same with bellow of fury and burning rage, only issue is having all these abilities, cause in WH2 there was a max amount of abilities a character could have and use. As such cutting the gates of khorne that the cultist has would be wise, and then either making it so you only pick one of the locuses, or only one between bellow of fury and burning rage. This will ultimately be a sorta nerf for the hero but it's more reasonable and isn't as bloated.

Next is Slaanesh, again bottom line should be similar to what was done for Khorne, but tweaked for slaanesh instead. Along with the locuses. Melee line is fine, magic lines should be condensed a bit, I know having 2 full lores is appealing but I think some changes can be made. Have it be Melkoth's Miasma, then enfeebling foe, the withering, penumbral pendulum, missile mirror, then evasion, then pit of shades, okkam's mindrazor, soul stealer, slicing shards (from slaanesh lore), then ends with greater arcane conduit. And for the last line have it start with feasting on fear, then spiteful conjuration, blissful rapture, earthing, soporific musk, glamour of slaanesh, whisper of glory, and then end with harvester of souls. Again spirit of essence and fate of forged are fine, ballet of blows and seductive glory are fine, the gates should probably be cut though.

Next up papa Nurgle, ditto once more for bottom line but for Nurgle, along with the 3 locuses. Melee line is mostly fine, just remove salyak's lullaby (doesn't need it), fetid stench and pestilent decay (moving them to final line), putting in foe seeker and deadly onslaught instead. Magic line is miasma of pestilence, then stream of corruption, earth blood, rancid visitations, curse of the leaper, then evasion, then flesh to stone, blight boil, regrowth, dwellers from below, then ends with greater arcane conduit. Final line, starts with nurgling tide, then children of nurgle, life bloom, earthing, fetid stench, pestilent decay, a passive regeneration skill, then ends with plaguefather's oration. Again spirit essence and fate of forged are fine, and remove the gates. Add abilities of virulent contagion and copious vomit.

Now for Tzeentch, this one I really don't know about, cause it's all summons and nothing else. So I'm still going to give my thoughts based on what I can tell from looking at the skills, but more so than the others, this would require playing a campaign to really know how or if this needs changing. Bottom line give him hero skills same as the others but for Tzeentch, give him the locuses, moving on. There's no melee line, this is fine, we'll instead say summon line, start with gorger onslaught, then bestigors, rotting prometheans, skin wolves, cairnwraiths, then add evasion, then war hydra, hellpit abominations, rotting leviathan, terrorgheist, then ends with arcane conduit. We're adding a magic line now, starting with spirit leech, then flock of doom, treason of tzeentch, vermintide, transformation of kadon, then prismatic plurality, then flame storm, savage dominion, comet of casandora, net of amyntok, then ends with greater arcane conduit. Final line, life leeching, bestial surge, earthing, syreens summon, ushabti summon, word of change, and then ends with gate of chaos (summon blue horrors), gaze of fate and hidden in time are fine. The other gates would then be cut out, spirit essence and fate of forged are again fine, and that's all. Add a skill dump to all of them for +1% hp per point for extra skill points for those using skill point mods (it'd unlock at lvl 30 or so).

And that's all I got, these changes do not need to be made exactly as I've said, I'm just giving my thoughts on how I'd like to see them changed. I also haven't checked avatar of Ursun and shade of Be'lakor, so I don't have any current thoughts on them. It's a great mod and even if my ideas aren't taken in I hope to see it do well and get better. Thanks for the hard work you've done on the mod thus far and will continue to do in future.