First off, Sus, I love you, you are amazing. Thanks for devoting some much of your time to something like this.
Ammo
Ammo in particular I find to be very underwhelming because most of them are only effects that add minor amounts of elemental damage. If the damage for ammo scaled higher, much higher than that of other weapons, especially as they are a limited resource, then I would see them more useful. I would also remove the material name from dropped ammo, and instead just put it as foo arrow/shot of foo - and let the damage range be based on the launcher using it - if possible. Also, there drastically needs to be an ego that raises range, either on the launcher or ammo, but preferably both. Along with that, none of the greater ammo egos strike me as particularly ... greater than any other ego.
Amulet
I also agree that if there is some limiter on double ego amulets it should be removed - I see no double ego combination to be particularly powerful. Also, mastery amulets being changed in the way that Sus suggested would make them better overall - less useless drops/finds, and less clutter. It'll make it 'easier', but then again, mastery isn't all that great anyway. Also, Shielding/Grounding/Stabilizing/Insulating/Cleansing needs to scale with mlvl because static numbers are never fun. You just look for one that is applicable to your character, and sell the items with that ego that are higher in mlvl than the one you are using to make more money. If they scale, then it'll make mlvl matter with jewelry.
Armor
I don't understand nature res on armor, sorry. Also, all the On Melee damage [Hit] egos MUST be raised MUCH MUCH higher than currently, and then scale way better to make them desirable in the least. They aren't powerful effects to begin with, as they only trigger when you would normally take damage, so if they are to be desirable on their own, then they need to deal some seriously greater damage than they do now. Also, ya, there needs to be no duplicate egos like Solid and Impenetrable - just make them a single ego with a higher low end than Solid, and a slightly higher top end as Impenetrable - because Impenetrable itself is rather low as it is now anyway.
Belt
All belt egos need to be almost doubled in effect currently to make them even attempt to compete with any of the artifact belts. Slotted should be removed as it's no longer really applicable.
Boot
Rushing and Disengagement shouldn't be greater egos as they are simple duplication of necessary talents for the classes that would use the boots anyway. They can still be semi rare, but they don't need to be greater ego. Phase on the other hand is very helpful to everyone, and is rather useful at that - so it should remain greater ego. Uncanny Dodging needs to be raised by maybe 1.5x for it to ever be noticed, and should scale much higher with mlvl - especially as there are only 3 mlvls that they can be generated on. I also agree with Sus again, stealth - while useful to those with the tree and are actually investing in it, is far too narrow an ego for everyone to get. Now, if it granted Activate for Stealth tlvl 2 or so, then I can maybe see them being more useful.
Studded or something like that might be a good prefix ego - making movement talents have additional range -those being rush/disengage/ghoulish leap/ect - so that it isn't TOO narrow of an ego.
Launcher
I don't see dex increasing from using a launcher, and having speed/greater speed is not good either. Just make a 'of speed' and have it scale with mlvl - with a base of 1.2x decrease in attack speed.
of Distance or Tensioned would be good egos for launchers as well, to increase the range they can fire. They are very short distanced attacks and having a way to increase your range should be very highly desirable. It should be atleast 3 more tiles at mlvl 1 and should probably cap at doubling the current range of the launcher. As such, it'd be a good greater ego.
Cloak
Stealth for cloaks applies the same way as stealth for boots. The 2 dual stat increase egos need to be 2 base, and scale up to at least 5 based on mlvl. 2 is too little, and anything more than 7 is probably a bit too much. Oiled and Thick need to be base higher, minimally 10% and ranging up to about 18% based on mlvl. Finding oiled cloaks that grant 4% res does nothing for anyone. I would also argue for plush to be renamed to something else and it grant even higher armor values + some physical save bonus and be pushed to greater ego.
Digger
Lighted could be a good prefix ego that adds a light radius.
of Mining could generate a chance to turn the tile into a gem once dug
Glove
I agree completely that either the elemental gloves need to grant some elemental damage bonus & res, or elemental damage bonus + branding - in both cases, they need to be higher than they currently are. Iron Grip needs to scale with mlvl and should maybe start at 15% less at mlvl1 than it is now. Criticals I think should be taken out as it only adds %chance and that's pretty easy to come by. Might Criticals should be a greater ego as it is, but the % it adds should be raised much higher, and should effect all crits, not just physical. I'd double it's current effect at least, and make it end up being about double that at the cap of range.
Helm
Again, don't see how a helmet can great dexterity... Prismatic needs to be greater than 10% for both, and it should resist both equally. I'd have it be 15% base, and max out at about 30% as there are so very few ways to get light/darkness res, and it's such an important res to get late game. I also agree that the energy regen egos need to be either broadened or grouped so that they are not so niche, especially as they are rather rare. Greater Telepathy should be Telepathic and made a prefix, so that you can have Telepathic x of Telepathic Range. I would also like to see a helm with an ego like Echoing - one that increases the effects of all shout/cry/ect type talents, ALL of them.
Lite
A mapping light would be cool, and it'd be even better if it's a prefix. Something like Ethereal Eye that activates for Vision tlvl 2 with the tlvl scaling with mlvl - and I'd like it if it granted a bit of see invis and see stealth as well. Scorching needs to deal way more fire damage - I wouldn't mind if it did 50 fire damage and it did 10 fire damage to me when hit. After all, that's one hot fire. A 'Dark Light' ego that removes the light radius completely but grants a medium infra vision [sort of like wintertide but weaker] but activates for illimunate.
Ring
Brawler's ring = ring of strength + ring of defense
Titan's ring = ring of constitution + ring of physical save
Duelist's ring = ring of dexterity + ring of accuracy
Wizard's ring = ring of magic + ring of spell save
These are drastic improvements. You could also remove the see invis ego and instead make a Seeing prefix that grants see invis/see stealth and maybe a slight blind res/will save boost. The regeneration rings could instead be grouped to regen ALL energies that would be normally applicable to have a regeneration effect. An 'Enhanced' ego could be tacked on as a prefix to raise the effective mlvl of the ring by 1 so that they have some prefix that isn't too niche.
Robe
I'd like a 'Flowing' prefix that gave the robe a greater def value as all robes are rather trash. And, instead of the various single elemental resists, I could see a single 'of resistance' ego that grants about 4 random resists at about 10% min ending at about 15% as a greater ego. If they were removed, this would make robes have much fewer egos though... so maybe just keep them in and implement this as well.
Shield
I could see nature resist replaced by light resistance. Spiked as an ego would be nice, but not just +phys damage, instead, increase the dam_range of shield bashes. All on melee hit should be raised just like with armors as they suck hard. of deflection is good but should maybe grant some serious ranged def boost as well, like a 20+ boost.
Stave
The damage boosting egos I believe should be limited to a staff that deals that damage type - an icy staff of fire damage doesn't make any sense. Shimmering should grant more mana. A new prefix, called Runed - which increases the damage that the staff does [effectively it's a +phys power for staves ego]
Melee Weapons
Massacre should probably be scaled more like what Sus suggested than what it is currently. As of now, you either have a shit bonus, or a stupid high one. A tool tip for of accuracy is probably a bit messy but it wouldn't hurt at all to have it for attack in the character sheet. Phase should be a fractional removal of armor, but should start at removing 50% of armor and should scale up to being about 90% armor ignoring. That way some random number doesn't mean a whole lot, but a % is easier to gauge. I'd also like a diseased prefix ego to deal blight damage and chance to add the con disease like poisonous has a chance to poison. Icy I think should be changed to frost and deal cold instead of ice, as it's unfairly powerful when compared to the other core brands. I'd also like sharp/spiked egos to grant physcut damage type - or better yet add that to massacre ego.
Wizard Hat
See other applicable things as they all apply here as well. Also, I'd like to see something like +arcane damage/resist or activate for a Blastwave style effect that does arcane damage.
All and all, I think we don't need too many new egos, but add them in as more classes come so they have something unique to grab hold of. However, almost all current egos need a serious rework.
Again, thanks Sus.