Went ahead and did a full game on a medium random map with each of the sovereigns in the current build to see if they feel unique now. These are my thoughts so far:
Hypnotism, Chant of Vitality, Divine Wisdom, and Earthly Familiar are all underpowered compared to the others. The Tyrant's Coercion is godly in a city already focused on production. The Tinkerer's Transmute is always useful, since you're able to trade in those (almost 95% of the time) useless bows for a shot at decent high tier gear. Hypnotism and Earthly Familiar both scale horribly, so by mid game they're all but useless. Anything you would want to hypnotize is basically immune, and the Familiars never seemed to improve. What's really weird is that the Guardian has Familiars as their representative ability, when Harvest Shadow Lands is one of the best spells in the game. Just switching the start screen to show Harvest in place of Familiars would make it feel like a better choice for sovereign. Chant of Vitality was rarely useful, and mostly seemed to exist to save on turns at the expense of mana. Changing that to a duplicate of Tireless March without the maintenance cost alone would be an improvement. The Priest's Divine Wisdom is probably the worst of the bunch, since a simple +1 is completely negligible. Even changing that to a +20-25% would make it useful and scale into late game.
Enchantment really lacks oomph. While those +1s to damage can really add up across all of the gear, it's just not interesting. I rarely found myself bothering to enchant anything other than my heroes gear, and usually I just stuck 10% xp everywhere I could. The other minor bonuses are almost pointless, since by late game the general strategy is to avoid having the other side move at all, rendering defenses moot. The resists are completely laughable, and just make you scroll more finding what you actually want.
The Tinker can't create Radiant Diamonds, required by all of the legendary items he can craft. Instead he gets Elemental Ash/Frost at the very end along with Platinum Ore, which are moderately insulting since they're just a fire/cold version of what he could already craft with Aspect of Lightning, only more expensive. In a complete playthrough on a medium sized map I found a total of 1 (one) Radiant Diamond, and I maxed out the Spoils of Victory chain before I went into anything else. So my tinker, where I spent 3 levels to obtain Legendary Jewelry, Weapons, and Armor, was able to craft one. Either he should be able to also craft the Radian Diamonds (albeit at a very high mana cost) or he needs to get a few free with the applicable talents. Spending an unlock on something you never get to create due to RNG is depressing.
Difficulty still seems to be set too low. I played all but two of the games on Hard, and the Tinker/Wizard on Insane, and never really had to struggle. I frequently forgot that dread was even a thing, as it never got past 50% in any of my games. While I have been playing TBS for decades, and this particular series since the original Elemental, it just never felt challenging. The very beginning is the only slightly scary part, but even then it's easy enough to pick up chests until you have adequate gear and start beating on weak mobs. By picking up the ring of the tutor I always had a max level hero by the time I started having to worry about any +threat from the Sorceror King, making his actions moot. Perhaps make higher difficulties also incur a logistics penalty, that might force a difference in playstyle.
There seems to be little to no point in ever taking anything from the Sorceror King, assuming doom mattered. If doom was an actual issue, then I would never take anything from him, because they're all incredibly tiny rewards.
Quests are almost never the actual difficulty they display. IE you pick up a quest from an Inn that shows it as Weak, and it has you go to a Warlock Den labeled Deadly. It doesn't make a lot of sense, and it can make it difficult to figure out what you want to hit early game. A quest should always lead to a quest of the same difficulty, excluding some kind of specific chain resulting in a nice reward (like the minor faction quests).
Spells in general are rather boring. I realize part of that is probably because I played so much Elemental, FE, and FE:LH, but I just find the lack of variety disappointing. You have your one basic direct damage spell that everyone starts with, one good AoE spell, city enchantments that require almost no forethought since it's so easy to get 6+ essence in a city, a bunch of generally pointless hero enchantment spells I never bothered to cast once, and then fluff. The summons were occasionally helpful to provide backup in a newer town that was being invaded, but otherwise they weren't worth the mana. The fact that minions can have gear and summons are basically naked make them very underpowered at pretty much all levels. Also I miss my lightning elemental's knockdown 
Sometimes I would start a game and my entire starting town would be in shadow land. This is silly, since it just leads to a restart and wasted time. Starter towns should never spawn in shadow land.
I'm really hoping we get a bigger variety in units by launch. Every sovereign has the same 90% homogenous units, and then a few special ones much later. And those aren't even always worth using, like the Tyrant. While it's nice that they each have a different starting group, I wish that level of variety spread out throughout the game, as the two lesser units almost always end up dead relatively quickly, and then you're back to heroes + archers/magicians/clerics.
End wall of text, that's everything I can think of for now. I'm sure I'll find something new when I go back through and try a few games on a huge map to see if that changes the late game sufficiently.
