I have to say I'm a little disappointed. The weapons are okay, but I wish we could select the debuff we put on the weapons, and maybe improve them from what we currently have.
These are my observations on the items. I won't touch almost any of the caster* items, because I don't play them as much...
1. Echo of the HeartCleaver
Baphomet Tactics is underwhelming, for two reasons: first, the bonus to tactics is worse than the combat bonus at level 15, and the extra damage is negligible — not worth the loss of DC. This needs to be 15, or even 16, DC to all DCs, and the damage needs to be better; it's a raid weapon. On top of that, the damage of 7d6 is a bad joke. If it were up to me, I wouldn't put a single item with 1d6 damage dice unless you raise it a lot — even 16d6 is low at end game without any sort of scaling — but 7d6 on a raid weapon, on an effect that's limited to bosses and tripped monsters, is almost outrageous.
So let's raise the DC to 16 and the damage to 30d6 (hell, maybe even try to make it scale with 50% melee power), and you'd have a decent effect. It won't make people cheer, but at least it won't make us cry — especially considering it's an effect that only works on tripped monsters, and even then it won't affect the damage of bosses at end game.
Telekinetic is a weaker version of Paralyzing. I think the only redeemable aspect is that you get the bonus damage from all those items with "+damage to knocked-down enemies." Either raise the DC, or add some damage to it — another 10d6 +50, or something, on a successful roll.
2. Butcher Mouth and Teeth
I'm talking about both of these weapons together because they're basically the same, which doesn't make sense — this kind of redundancy shouldn't exist, since both are blunt weapons used by the same races and classes. In fact, lore-wise, the Teeth should be a piercing or slashing weapon. So I would try to differentiate them more, since I think it's too late to change the Teeth's weapon type. If it were up to me, I would make the Teeth deal slashing damage instead of bludgeoning.
Other than that, my only issue with these weapons is Yeenoghu's Butchery — a wasted effect on a raid weapon, mostly because it's so easy to slot enhancement double strike onto any other piece of gear, even yellow augments, if you still want to keep up the double strike bonus. Make it unique 3–5, stacking with everything, and please raise the damage to at least 16d6, or a bit more, like 20, since it's also a more limited effect due to Paralyzing. That shouldn't be at the same level as Baphomet Tactics, since this effect lands more easily than Trip, but it should still be better than an augment at level 24 that's already lackluster.
3. Butcher Tongue
The same issue as with Mouth and Teeth, but at least this one is used by a couple of other races.
4. The Deep Father Fang
A better version of the previous weapons, mostly because we have Metalline, a good effect on any weapon — but also because of the damage. The only bad thing is that this shouldn't have Legendary Ash, since it's a physical weapon, not a caster dagger — something that reduces PRR should be here instead.
5. The Faceless Lord
Overall, a good bow. I wish it had Paralyzing instead of Disintegrate, considering the bow is a slow weapon, so you won't get many procs. Aside from that, a solid bow, and probably worth considering as an upgrade.
6. Fetid Prince
Another solid weapon, sadly on a weapon type that's pretty much useless, and a proc effect like Disintegrate is wasted on a two-handed weapon. I wish this kind of thing wasn't used here unless you get a special version with more damage or a better proc chance, because the value of this effect changes a lot depending on the weapon. Two-handed weapons need effects of their own if we ever want to see them return to the meta.
7. Slime Father
Quarterstaves have better support than Mauls, so this weapon is immediately better — having Blunt Trauma gives this QS a chance to dethrone the Staff of Shadow as the best QS in the game. Sadly, two-handed fighters (THF) are still in the dust DPS-wise, and there's nothing here to fix that (I must insist THF should have more effects, and/or better ones, than one-handed weapons).
8. Diadem of Rot
This item has two issues. Natural Armor is a very common effect for tanks (the main target here), and it's mostly useless on non-tanks anyway, so a different effect here could do a lot — maybe Insightful Amplification of all types, a rarer AC source (like Primal Hide), or Quality Sheltering could work. A legendary version of Hardened Exterior that gives 5 AC or more would also be welcome here (we haven't seen an effect like this since Feywild).
And then there's Improved Demonic Shield — a 120 shield bonus on a level 35 raid item. I want to believe this is an error and it was supposed to be the legendary version, but even so, it's a weak effect for a raid tank item — it should have Legendary Affirmation.
9. The Queen of Rot
Fortitude 14 is a hard no on raid items — it's too niche, and most tanks would rather have a Resistance 12 item here, as others have already said. Freedom of Movement (FoM) is a very common effect that's already on a lot of tank items, so I'd rather see a different effect here — maybe absorption for one of the raid's damage sources that isn't covered by the other items, like an alignment absorption, for example — Evil Absorption hasn't appeared since the level 29 items. That way, every tank in the game will want this item for the raid, at least.
10. Skull of the Horned King
Maybe change Double Strike for another, less common offensive effect, like Cannith Combat Infusion, which hasn't been seen in a while — maybe a legendary version with better numbers, or one that adds some melee power, or just a better proc chance, maybe 5%.
11. The Volley's Aria
Oh lord, what to do with this item. It's clearly an item for an Arcane Archer or a ranged character using Sonic Imbue (Bard), but honestly the game doesn't support either of those playstyles anyway, and unless you have an AA rework planned soon, this item is dead on arrival.
What I would do to try to help is forget about Insightful Enhancement Focus and swap it for Quality Frozen, Thunderstorm spell power, or at least Insightful. This way the item would still be focused on ranged characters, but wouldn't be a must-have item for casters of those schools, since they'd be wasting two slots — not ideal, but at least there would be a place for it. Give it a new doubleshot source bonus and you'd give this item a chance on regular characters, with one big drawback: a lot of useless effects for most ranged characters.
12. The Prince of Demons
Here's an idea — be brave with me and make this item give 20% attack speed when using a two-handed weapon. Give THF some love.
If you don't feel brave (or "stupid," as a Kobold would say), remove the attack speed and add another effect instead — an updated version of Rune-Fueled Warding giving, say, 50 DR for THF, or an updated version of Bloodrage Defense giving 15 PRR/MRR for THF, or combine the old effects into one.
And please upgrade Legendary Conditioning to at least 10% (it should be 15%).
Also, go crazy and add Dipping with Magma to it, and barbarians will go crazy for it.
13. The Sixth Toe of the Shadow King
Oh god.
It's a caster item, but most of the time you won't be close enough to other casters for the silence to ever reach them — and that's assuming the item's proc chance is even decent enough to matter. Please remove it and put something else in its place — take this chance to add Quality Sonic spell power to an item, for once.
Smoke Screen 40% on an item that's most likely going to be used by a caster with access to Displacement? Please remove this and add something related to sonic damage or bards. You could even end the item's lore by saying that, for some reason, the toe is always trying to keep the same rhythm — maybe it wants to drive you mad? — and change the quality spell DC, since it doesn't stack with the Quality Enchantment DC that's already on the same item. Make it a profane bonus to Enchantment DC +4, or a +3 to everything to save a player an augment slot — bards know they need every solar/lunar augment slot they can get.
In short, do something about this item — it's really bad for a raid item, and especially bad for a caster item.
14. The Unbreakable Divinity
Extra smites are fine, but Hollowed? On a raid item? Please, until you actually make Turn Undead useful, stop adding this to raid items — leave it as a quest item, if at all. Instead, maybe add an effect that gives 1 damage or 1 melee power per 2–3 Religious Lore feats, as a poor man's version of the Sanctified Fervor filigree effects? I don't really like Quality/Legendary Deadly, since there are other really good items in the expansion with the same effects that you'd never drop this one over — and this is a raid item, so it should be better.