Alright, this is mostly a faction tier guide with some commentary and feature requests thrown in. If people want to comment and give useful info on the factions I'll adjust the rankings. I'm coming to CoE from the Dom community where the meta's at a much higher level, so just gonna provide some basic info here from 20-30 hours of basic faction playthroughs. I also have next to no experience with the other planes, so please point out if something that happens there changes a faction’s tier.

My experience with the game so far is that in general, gold-based factions with a couple of good basic units are the strongest in the meta. A lot of the rituals only become really useful later in the game, when most of the good settlements have already been secured. And the highest-tier rituals are often crazy expensive compared to the value you get from them. Good troops > good early/midgame rituals > good lategame rituals.

Voice of El. This plays as a pretty standard gold-based faction, as relics don’t do all that much for you. Mostly you want to spend gold on calling the Inquisition, a very high-quality army that moves on its own taking settlements, worth easily twice the 250 gold you pay for it. Being uncontrollable is a huge pain, but eventually the Inquisition stops moving and you can take control of it with a commander. At that point it will often still have troops worth over 500 gold, after having taken settlements for you. Additionally, after paying 250 gold once to upgrade your Arch Bishop to a Cardinal, you can recruit the incredible Templar unit. For 50 gold, 15 resources (easily traded for, or produced in mines) and 5 relics (which shouldn’t be scarce) you get a unit with 2 attacks and a charge, 3 armor and a shield, and 16 hp - almost triple basic infantry’s. They’re also blessed, which can come in handy later but often doesn’t do too much for them. It’s hard to overstate how good these guys are. They give you easily double the value of most other troops with absolutely no bless, allowing the Voice to outcompete the other factions in typical battles. The Voice has trouble with some high-tier units and certain players can lock out their walled settlements with good siege/ranged weapons, but he gets good conversion and banish magic and often picks up a few powerful casters with the Inquisition armies.
High Cultist. Tier 1-. Weak start, but if you survive the lategame units are very powerful with high-damage ranged attacks. Best lategame I’ve seen so far.
Maybe Baron. I haven’t played him since his mechanics looked very bland/straightforward. The freespawn seems powerful, he’s at least Tier 2.

Senator. Similar faction to Voice of El, with 50% more gold but no comparable units to the Templar and no Inquisition ability. Their ultimate ritual’s fine. Not a super exciting faction to play and suffers in the lategame from lack of powerful units.
Bakemono. Gets ok freespawn from mines, and recruitable Dai Bakemono Archers are a decent support unit for the freespawn, making solid armies. Rituals may or may not be any good.
Priest King. Average to good troops, average to good rituals and good magic variety.
Witch. Starts off with weak units and 0 gold income. If you can reliably take forests the fungus income is solid for summons - be careful as they can turn against you. Recommend increasing the sacrifice percentage to something like 120 regularly. Troops are lame but spearmen+summons give you decent mid/lategame potential. Micro-heavy for sacrifice percentage adjustment, gets weak necromancers through manflayer random recruitment that can help you use towns effectively.
High Priestess. Average troops, unclear on the value of the blood desert rituals. Sacrifice rituals give good power - should be saved for lategame, when they’re more efficient and don’t hurt long-term income.
Troll King. Poor starting location with 0 income and no mages, but troll king is a good combatant and goblins are good recruits. Rituals are bad early-midgame, but troll shamans are good mage chassis. If you can keep your troll king alive he’ll pay dividends over the early-mid game and allow you to bully AIs. Might be Tier 3 faction depending on how lategame magic shapes up. Trolls are very expensive in iron but if you find good mines are worth it. Also worth trading for iron.
Necromancer/Markgraf. Played a little, the undead summons seem decent. Not sure how they shake out in the lategame.
Pale One. Played a bit, troops are slightly above-average but summons are very expensive.
Burgmeister. Haven’t played as them, but horticulture summons seem decent from fighting the AI. Troops are costed well too. Maybe Tier 2+.
Barbarian. Played a little, troops + summons seem decent.
Demonologist. Haven’t played, just assuming bc demons are decent in Dom.
Enchanter. Haven’t played, assuming average. Could be bad.
Warlock. Average troops, average summons. Wasn’t impressed but there might be particularly good rituals I missed.

Dryad Queen. Can be good in the mid-lategame, but has very weak start with only satyr freespawn and is dependent on random commander recruitment to get better units.
Dwarf Queen. Tier 3+. Strength varies heavily based on luck, as they need iron or better mines to increase their freespawn rate and nearby mines might have other Dwarf Queens that get stronger over time. If you can get a couple mines going early on, you're good. Very micro-heavy to upgrade individual dwarfs with Rune Smiths.
Illusionist. Summons seem bad. Confused about how exactly they work with mirrors so maybe there’s a good option hidden in there somewhere.
Druid. Bad starting settlement with 0 gold and 2 fungus. Summons ok but not good, troops average to bad. Druid apprentice commanders are either rare or I got unlucky. Similar playstyle to witch - income is higher from jungles but the summons are significantly worse at the top end. Also lacks the witch’s access to necromancy.

On game start, resource multiplier options like in Dominions. This would make playtesting and playing against AI sooo much more fun, and probably add to multiplayer fun too.
The game remembers which settlement you last recruited from, and keeps recruitment on that settlement by default until the player selects another recruitment center. Alternatively, the game defaults to recruiting from the last settlement with a commander you selected. Either of these would be a big improvement over the current system that defaults to your home province.
It’d be great to have an “automate commander” button where they just start moving like they’re AI-controlled, like with the Voice of El’s Crusade or Inquisition armies. People wouldn’t use it much in multiplayer but it could be a lifesaver in singleplayer games for limiting micro.
Allow multi-turn move orders (interrupted if they’d hit an enemy army - there’s already a nice UI feature for this where the future path is mapped out when you click once. Selecting the next commander should just leave that order in place.
This affects balance, but allowing two units to be recruited per turn in recruitment centers instead of 1 would significantly decrease micro. It would significantly increase the playability of the game in both singleplayer and multiplayer, yes it affects game balance but the player experience improvement is worth it. Settlements are most OP when players have had plenty of time to recruit lots of mages or siege weapons, which this wouldn't change much. If balance is a huge concern, it could be alleviated by lowering the HP of settlement gates or adding more gates per settlement level.