The one change Dom2 really needs.....

[Cohen]

IMO Fever Fetish are too costy in that mod, probably they're alredy fine since Fire Gems are most used to overpriced remote spellcasting (well at least Fires from Afar is overpriced, it should cost 5 F.Gems)

The heavier effect are Blood Stones, for what regards the gem generating item. This prevent a Nation like Abysya to come to Hammers.
Blood Stones are forged by a Warlock + Earth random pick, to get E2, and then E.Boots, so E3 -----D Hammers
This is a far heavier unbalance for that nation depriving it of her only way to reach hammers (except pretender).

After, about Clams, I'd make them W3. They're a source that allow you to exchange "nature" of gems. You need astral, so probably you're lacking astral. The gems used are always 20.

Staff of Storms, IMO it should be construction 6, and 4 Air, 40 air gems. This because an Air Mage to cast Storm in battle, should be A4. So to fill a staff with the power of the storms, it should be theorically able to cast the spell.

Flying Boots, A2, 10 gems it's good.

Draining Life Weaponry:
Wraithsword, D3S1 IMO and so 20 D.Gems and 5 Pearls.
Why S1? I've took idea from the Soul Drain (the D4S4 spell). And const-6. This make it difficult to forge too.
But even D3 is good.
Hellsword, it has the hindrance of berserk if wounded ... a bad stuff for an SC that perhaps get a scratch from an arrow. B3F1 20 slaves 5 fire gems.
Blood Thorn, this is more difficult to set, because it gives too 1 point in Blood. 2 Nature imo it's too much, perhaps B41N 40 slaves 5 nature is better. Or B31N.

If you made your Item mod with Blood Stones and Blood Thorn as you previewed here, Abysya will fall so down... losing bth items from their base forging range.

Many items indeed should be less costy, like Stone Idol, the Crystal matrixes, the Stone Sphere and such.