Joining the discussion here on how Seraphon look and feel, I will preface by saying I've played precious few games of AoS, with 3 being my first foray into GW after having played 40k 5th and 6th edition well over 10 years ago
However, I think that we largely have to temper our expectations, as GW did say they were making most things across the board a lot weaker. I believe this also comes at the cost of a lot of rules feeling watered down, same-ey from faction to faction, and so forth. I think it's helpful to try to look at the rules in relation to other armies, not comparing them so much to AoS 3 versions. I'm not saying this is a *good* thing, but it does leave room for some inevitable power creep when the battletomes are released and as AoS 4 progresses.
Especially after seeing the Ironjawz battle traits, hoo boy. A 3" move for one unit and then the once-per-battle Waagh? Now THAT is pretty boring imo. I'm actually really happy with where the Seraphon are at with our asterisms, we have so much adaptability with it. The ability to choose our asterisms at deployment and not at our list building is such an interesting trait, in my humble opinion. We can tailor them both to our current army and the opponent we're fighting in the moment.
As for the conversation on spells being extremely short ranged and rather benign...yeah there is definitely merit to those opinions. I think that not seeing the rest of the spells available to us doesn't help, especially as Earthquake for example might still be the "draw a line from the caster to the corner of the map" range. Also, with Arcane Vassal still existing (albeit once per turn) and at an 18" range, AND our Astrolith (hopefully) increasing spell ranges by 6", we're looking at the slann potentially being able to cast a 12" spell on a target 36" away. That's pretty good.
And although the spell revealed is pretty bland, removing some rend, I think that there is a bit of silver lining here. First off, it's -1 rend from *all* the target's weapons when it certainly could have been just one, which would have been a lot worse. Secondly, being able to be cast as many times as we have wizards is quite powerful.
I know this is a bit of an optimistic, optimal-scenario take, but let's take a look at how this could be stacked on, say, a unit of 10 warriors on an objective. They're a 3+ save due to their warscroll (if it's the same as Spearhead), and the new Mystic Shield can be cast on them to give them a 6++. If we have them wholly within our territory with the buff from the Quetzl the Preserver (-1 rend), and then have two other wizards cast Mystical Unforging, we're looking at a unit of warriors with a 3+/6++ and -3 to rend for melee weapons targetting them. That's really quite good I think, and of course it's under optimal conditions, but I can't say I've seen any other faction with an unlimited ability to stack -1 to rend on all weapons.
After watching Caleb Hasting's video with his thoughts, I've warmed up to the Carnosaur a little bit. I'm a bit salty it's still not the apex predator that I want it to be, but I guess it filling a role of "monster killer" is fine. Seeing how much more of a monster killer that Gordrakk and his mawcrusha are is a bit disappointing, though I'll withhold judgement until we see some point values. I was also initially excited to see that the terradon's rock-drop ability was more than once per game, but I think that's been a bit tempered by running the math on their ability. They certainly fill a role being hyper mobile, having up to 16" move with the asterism bonus, but seeing as GW specifically said they're trying to limit the amount of mortal damage in the game, I can't say I'm too surprised to see that their rocks aren't a serious source of damage. I imagine they're best used to harass a few units they fly over and throw some javelins while spreading out to take some distant objectives/battle tactics/prevent enemy reserve units from dropping in. If you have a unit of 6 terradons and the chief (if the chief is about the same as current), you'll be dealing approximately 4 mortal wounds per pass. Which, while not a lot, is also par for the course for fewer mortals this edition.
Overall, I'm most excited for the kroxigors, who seem to have an actually *really* good battlescroll. I guess you can call me a bit of an optimist, but I can't wait to see the rest of the faction. I think that GW could have done Seraphon a lot more dirty than they did, whatever our individual opinions might be on the rules.