So had a couple of games on the weekend with the deepkin.
I dropped the Namarti Corps battalion and merged the Thralls into a single 20 man unit. Totally worth it. The flying Turtle did very little damage output wise in both games, but the extra save was solid, and the combo of the turtle with lure light meant I could engage in a war of attrition against 30 chaos warriors lol. It's odd to have tanky elves
Some of the Endless spells are undercosted. Right now, if you don't field Wizards or don't have access to units that can atleast dispell, you're in for a bad day, even if you have access to those, you can still some up against casters you can't stop due to load of bonuses they get to cast, not fun to simplay have to take 2D3 MW a turn with nothing you can really do about it, it would certainly suck worse for armies that can't regain models. Mortal Wounds are still problematic, seems like it would be a fairer system if they moved it to auto-wounds.
It is strange 40k has removed the Turn 1 deep strike, because it caused a boat load of problems, but still allowed it to happen in AOS.
I don't think Namarti outside of Mor'phan are worth it, they just get torn to shreds otherwise.
The warscrolls for Bretonnian's seem to be woeful versus anything with a codex, not sure if this is for all the old armies.
I will say, that larger units are always better than multiple smaller ones. Just keep in mind, the bonus save for being in cover, doesn't apply to assault.
I think for the most part, the endless spells are pointed well, except for the geminids of ulgish, but they did faq it and the spell portals to limit their effectiveness. You do want wizards though. A good counter to endless spells is the lense of refraction artifact from the realm of light as well.
Turn 1 deepstrike was mostly an issue in 40k, due to shooting. In aos, if you plan for it, turn 1 deepstrike is not an issue, and a lot of factions are quick enough to charge across the table t1 anyway. Screening units are critical for success in aos to mitigate both of those things.
There is a bit of a power imbalance between battletome books, and those without. But, it's more due to a lack of battalions and allegence abilities, more so than the warscrolls/points. Some factions with limited options (like thunderscorn) do struggle, but quite a few "have not" factions can hold their own successfully.
However, compendium units and factions are purposely neglected. Games Workshop doesn't sell brettonia or tomb king models anymore, and don't want people trying to buy second hand models in an effort to chase the Meta. The pdf rules for legacy/compendium units are clearly only there for people holding out with their old models. Unfortunate for those who still have those models, but at least they can still use their toys.