v3 is much, much better. I made some notes as I played as you asked for feedback. Some of this is more nitpicky than others, but I generally made notes about things I thought could be more fun or interesting, or when a choice was obviously the wrong one. I apologize this is a bit long, but hopefully you'll find at least some of it helpful.

General Points:
*** My Chaos Sorcerers mounts were not working, but this could very easily have been a mod conflict. Next time I boot up the game I'll check with no other mods enabled.

Chaos Chariot is more expensive than Gorebeast Chariot once skilled.

Archaon-only: Dragon Ogre Shoggoth and Dragon Ogre upkeep way too low, eventually going to 0 with legendary gear. No idea why this was specific to Archaon, though as with the mounts it may have been some weird mod conflict problem. They worked fine on other lords.

Troll upkeep never changes and they aren't very great to begin with, making them extra useless. The armored troll building is particularly undesirable because of this.

Losing army-wide Vigor reduction is a pretty big hit for Chaos in the campaign, I'd suggest replacing a skill in the non-specialization tier with this. I'd recommend either Foetid Aura as
Vigor seems like a Nurgle thing, Archaon has it as well as the other lords, and it's pretty worthless (though a cool idea)

Might be kinda fun to give Archaon a Chaos Dragon at some point, for sheer cool factor.

The +5/10 exp/turn on the Palanquin building is really, really minimal. That's about how much 1 Wood Elf Outpost gives the entire faction. Vlad Von Carstein gives something crazy like 200. It doesn't need to be near that high but 5 is close to value-less.

You might consider adding corruption/corruption osmosis to chaos ruins. I realize there are mods that do this, so take it or leave it, but I think it's a bit weird when you leave an area and the Chaos corruption stops even though there are a bunch of portals and destroyed cities.

General lack of any skills that buff monstrous units, though an all Shoggoth army has basically always been the way to go in Chaos Campaigns, so maybe this was a choice you made on purpose to encourage other builds. It just feels kind of weird, but maybe one of the weaker skills might be replaced with this.

Skills with no reason to invest multiple points (first point is useful, others are not):

*Writhing Flesh: already has crazy high leadership, won't break until you've lost, 5/10 more makes 0 difference.
*Swords of Chaos (this may be Archaon specific?): Couple points of charge % aren't worth additional points.

Skills with no reason to take, ever:
*Marked By Slaneesh (Sigvald specific), see Writhing Flesh. My suggestion is it should give +speed instead. If he keeps no mount, you could make it a pretty high amount as well, like 10/20/30% or 15-45. Having him be crazy supernaturally fast would be neat. The fact he gets staggered by all large units has always made him the weakest Chaos LL, so maybe super speed would make him more unique.
*Frothing Berserker: With the +12 from Blood for the Blood God that everyone will take, MA is generally high enough to have a 90+% hit chance on everything except duelist lords. Not worth taking a massive defense hit that severely impacts survivability for what is realistically a minimal hit chance increase. Not sure if you are familiar with the hit formulations (base 40% when equal MA/MD, +/- 1% per point difference. Most lords/heroes have well over 80 MA with a single weapon and 3 ranks Blood God, and very few units have more than 40 MD), but I suggest entirely re-thinking this skill, as losing MD on these guys is pretty terrible so the upside needs to be amazing.
*Shimmering Armor: Extremely weak compared to the other two skills that are very powerful in its tier. 15 armor for 3 points is about 7.5% survivability at best, and it's not army-wide. Compared to army speed and infantry +MD it's pretty awful.
*Foetid Aura: Fun and creative idea, but in practice I can't ever see this being worth taking. Having the enemy sit around in a non-garrisonned position to take attrition damage in your local area simply doesn't happen regularly enough to ever be worth worrying about.
*Touched by the Plaguelord: Disadvantage is worse than advantage considering every chaos unit other than super low tier stuff fights virtually to the death.
*Nurgle's Gift: I've never waited out a siege in this game and I've got a crazy number of hours... this is not helpful. Buff monstrous units or chariots or something instead maybe?
*Unearthly Beauty: Bad for the same reason all the leadership stuff is bad with Chaos, you simply don't need it beyond Marauders, and these skills are quite deep and you won't be using Marauders. I'd re-think this one.

Anyways, it's already a way better experience than vanilla chaos, so keep up the good work!

Brilliant, this is *incredibly* helpful.

All of your general points are completely fair. I’ll check out the Sorcerer mounts – no idea why that’s happening. Did you pick Kholek as your starting lord, by any chance? The 0 upkeep for dragon ogres was probably Archaon’s items stacking with Kholek’s faction wide buffs. I’ll fix that for the next build – maybe I’ll replace Kholek’s lord effect to buff monsters somehow, and deal with another suggestion.

Re. specific skills: you’re spot on about all the skills that affect leadership. I’ll admit that at least one of those was just a placeholder that I forgot to change. Oops.

-Swords of Chaos and Marked by Slaanesh just use the default CA values for those skills, and I was vaguely aware that they were a bit crap. I’ll do something about them.

-Frothing Berserker: yeah as I was playing through my own campaign I was starting to realise this could use some more work. Maybe extra AP or splash damage instead of melee attack?

- Nurgle's Gift: this was inspired by my experience of the Beastmen campaign, in which you can get most garrisons to start taking attrition damage after a single turn using the right combo of hero skills, lord skills and techs. I found it a godsend in the late game, as it seriously reduces the tedium of fighting endless siege battles. Maybe I’ll bump it up to 3/6/9 so the effect is more immediate.

-Foetid Aura: I’ve actually found this to be quite helpful, as it offers you a way to punish the AI for sending stacks to chase you round the map. Combine it with the weaker version that heroes get and you can do some serious damage, even in a single turn.

What I’ll probably do:
- Add vigour reduction to Touched by the Plaguelord, ditch the penalty, and swap it with Bloated Monster.
- Buff Nurgle’s Gift
- Rethink all skills related to leadership
- Reduce base chariot and troll upkeep
- Change Kholek’s faction-wide bonus (maybe -1 recruit time for all monsters)
- Buff Swords of Chaos (maybe an additional -1 recruit time recruit time to Knights)
- Buff shimmering armour to +30 at top level
- Rethink Frothing Berserker

Thanks again for your time.

About the upkeep problem - can I suggest to you the solution I'm working on in my own project ?

Make a scalding upkeep faction-wide *penalty* that goes up with high-level buildings, main chains, and *per horde*, countered with horde-wide benefits from skills and buildings.
So you can play either with a chosen disciples elite guard and fanatics, that costs you nearly no favor (once levelled and boosted), because they are devoted to you ; or play a bigger game with more forces but high upkeeps where the added boosts just make them bearable.

It also makes the early-game spam of hordes impossible - you need the lords to level up before growing many strong troops in them.

To avoid late-game blocks, make the same high-level buildings and skills give some levels to the new lords.

Hey, I've been playing with this mod for my latest campaign now, I'm around turn 150. I like it a lot and it makes chaos play far better imo.

One thing I'm having trouble with though is making my heroes/lords good duelists. Lowering their melee defence (khorne tree) makes them more of a glass cannon and they are having a hard time winning those fights. I'd suggest that you incorporate more of the "standard bonuses" (like vanilla armor bonus/melee def/melee attack and so on) in your tree somewhere so the pathing is different but still possible to get. I also miss the standard activation skills from the yellow tree, but if you don't want/can't incorporate those in your mod I completley understand.

All in all these are minor issues I have with a great mod, thank you and keep up the good work! :)

Enjoying the mod so far. I initially played with it after playing Vanilla Chaos. Now that I have more time with this I have an adjusted perspective.

Swords of Chaos looks fine to me. Not sure why anyone would spend the points to max it, but Archaon doesn't have all that many skills compared to everyone else.

I'd initially thought Nurgle's Gift was overpowered (-3/6/9), but not sure I do anymore. Considering how easy it is to get Hellcannons, and knock down gates with them, I don't think Nurgle's Gift is all that anymore. I actually ran a short campaign to completion both with and without a heavy investment in the Nurgle tree as Sigvald, and I finished the one w/o Nurgle's Gift like fifteen turns earlier.

I still think the Chaos Undivided skills that render all your armies immune to attrition should only affect the army of the guy who has it, though thematically it should affect all armies if it's on Archaon.

I agree that it'd be nice to have some of the activated abilities from the default yellow tree. It's fun to have something for your hero/lord to do in a battle, rather than wading into the melee, and staying there.

It'd be nice if more of the units were gated behind other buildings. I like your idea of making them all available, but really expensive, but 1) this does make the other buildings less attractive, and 2) it makes it really easy to access some of the units that trivialize the campaign. Hellcannons are the worst offender here considering they're kind of an investment in vanilla.

Lastly, I kinda don't like Sacking and Razing in a single action. I still believe that you should take an income hit if you want to do it, and the option to always sack but not burn should be available. Sack & Raze is part of the reason I can regularly finish the short campaign before turn 100. Worse, razing always burns all your movement, and since you must raze a settlement you've attacked you must always end your turn after attacking a settlement. Similarly, the option to do nothing after subjugating a settlement should be available. It would almost never get used, but it's nice to have the option to walk.

Thanks for what you've done so far.

This is a great mod, indispensable for an entertaining Chaos playthrough.

Have you considered asking Duck_Bird if you could integrate some of the God-themed spells or abilities from the Marks of Chaos mod http://steamcommunity.com/sharedfiles/filedetails/?id=728172778&searchtext=marks+of+chaos ? There's a decent amount of overlap in what these mods do in terms of statistical mark effects - but the access to God-themed spell lists for sorcerors and non-sorcs who take Marks of Tzeentch and some sundry abilities could help further enrich the distinctions between paths and maybe spice up some of the blander/ more underwhelming abilities (the Nurgle attrition/siege reduction stuff comes to mind, several of the post-Hedonism Slaanesh skills are decent but unexciting compared to their analogs in other trees). Not to mention that it'd be much more interesting for Chaos Sorcerors to have access to the actual Lores of Chaos, rather than only the same magic the Empire uses.