Feels good to be the 1%. I used the victory conditions overhaul mod, though, I don't have enough patience for the RoC campaign, and only went for one of the short victories (destroy all Khorne factions). I got it at around 85 turns, which the modder says is normal for each short victory. One of the others is technically faster and I would've gotten it waaay sooner had I realized you can't vassalize your military allies. Anyway, the gameplay feels much better without the ridiculous RoC mechanics and the AI is much more aggressive. There was a complete bloodbath around Kislev and Norsca. It was the Norscan tribes vs Demons of Chaos vs Kislev. I didn't participate in that, though, because I went after Khorne. Once you get Exalted Daemonettes and Fiends of Slaanesh, Khorne is easier to manage due to the armor piercing (if you don't have a shadow caster, which I didn't). I'd say Slaanesh is ok on the campaign map, the devotee armies you can summon can help out in a pinch and I had to use one to successfully siege Skarbrand's capital of Infernius. The cult of Slaanesh, however, is a mixed bag. You can expend devotees to instantly create cults in random human or elven settlements on the map, then you can use that to build buildings that mostly generate more devotees or increase relations, but can also be used to destroy the cult and create an army in that settlement. I never used this tbh because I was neither strapped for devotees nor for relations, gaining an army in a random settlement was never really all that useful.
Like Cathay, Slaanesh's mechanics aren't extreme enough, with the possible exception of the devotee armies that you can summon next to a lord (not from a cult in a settlement). The mechanics are extremely limited also due to the extremely limited nature of the campaign map itself. If there was more stuff on the campaign map to do, the mechanics could've been more diverse. Again, look at Troy, you have at least 5 different resources to manage and collect (Sarpedon has 8 and you could get more depending on which mythological beast you've chosen) and you have the cults of the gods. This creates a nice baseline for everyone and then you can build faction mechanics around different things. In WH3 on the other hand, you only have gold as a baseline and nothing else, which means they will eventually start running out of ideas for faction mechanics. Which they did and that's why they started adding different resources for different factions (meat for Skaven and ogres, slaves for the dark elves, skulls for Khorne, devotees for Slaanesh and so on), but they always feel a bit tacked on and foreign. If we had 5+ resources to worry about baseline, not only would that help with balancing army composition, but it would give everyone stuff to do on the campaign map and then adding unique resources for some factions would shake up the game considerably more because there's exponentially more stuff to take care of.
I suppose complaining about how the campaign map feels barebones is a lost cause and pointless at this stage and I don't really have much more to say about Slaanesh. The battle gameplay is admittedly very one-dimensional with the Slaanesh roster, even more so than is typical in this game. The only viable army composition in the beginning is daemonette stacking with an optional sprinkling of marauders here and there. That's because cavalry is, surprise, surprise, useless in this game and chariots aren't working correctly atm. Once you get access to higher tier units, there are a bit more options (Fiends, Exalted Daemonettes, Soulgrinders, Keeper of Secrets, theoretically chariots), but the gameplay is still essentially one-dimensional. I think I got my fill of this game for now, I'd rather play Troy or Rome Remastered when I get the itch to play a TW game. WH3 (and probably this whole trilogy) is a bit too simple for my liking without mods and the gameplay mods that are available are dubious. I guess we'll see what they do with the combined map.