Gwyn chan 'r Gwyll

Oof, what model is this? Where is this from? It's an amazing mish-mash.

Looking at the new Cypher Lords models, does anyone else think they'd be great with some kitbashing for Idoneth? Lop off the braid, stick it on their shoulders, switch off their head for a Namarti head, and boom, variant Thralls. Use the heads along with the spare heads from the Akhelian Guard kit to headswap some other allied-in heavy infantry (which will likely get better when the new Cities codex drops). Headswap the Thrallmaster model with some other head, and you have a new Soulscryer or Tidecaster! Some of the Splintered Fang models could be decent for conversions as well, with their helmets and scaled armour What do you guys think?

Agreed, the domination of heavy cavalry would make sense in Warhammer Fantasy, but not in Age of Sigmar. Warhammer Fantasy was more grounded in history drawing more on traditional block-of-troops historical wargames. Age of Sigmar is heroic high fantasy, more character-driven, focused on skilled and differentiated infantry. Heavy Cavalry in this kind of setting is closer, I think, to the Hellenic era cavalry that swarmofseals refers to, where it's role is yes as damage-dealer, but only against the right targets and in the right circumstances. It shouldn't be able to destroy any heavy infantry, or any units that are geared to fight larger monsters or anti-cav units. This is because the main weaknesses of heavy cav (maneuverability and the need to have a long straight charge) can't really be shown in a skirmish wargame like AoS like they could in Warhammer Fantasy.

Luckily, the units you don't like or have budget concerns are all either bad or just inefficient. Reavers are bad as well, but you can easily mix Thralls in with Eels and keep a competitive army, though maybe not a tournament-winner like with full Eel lists. Shipwreck is free points-wise: it won't hurt anything but your pocket-book. No word on new units unfortunately. Hopefully we get an Underworlds warband soon though, could use some more sculpts at the very least.

I haven't tried it out, but I've been partial to the idea of running Scourge Privateers as a first-line missile-shield. 200 points for 20 Corsairs and a Fleet Master leaves you with 180 left for another unit of your choosing (noting that the new General's Handbook is expected to raise the Morsarr to 180 or 200, so you want a little wiggle room in your list for that). While Corsairs may not benefit from Forgotten Nightmares, they still act as the "closest enemy unit" for Forgotten Nightmares, so are a pretty cheap meatshield for the rest of the army, while getting rr1s against attacks in the Shooting phase. 5+ rr1s still isn't great, but it's better than your Namarti will have, unless you hide them with a Leviadon. Alternatively, you exactly have the points to fit a Leviadon in there, which is a pretty big defensive boost for your Namarti horde. 30 Namarti Thralls with a Soulrender and a Leviadon are pretty tough, especially if you make then Morphan.

Yeah, that seems to me to be going too far from "top tier unit in an upper-middle faction" to "scarcely useable in a lower-middle faction"