Actually most of these are non med so mainly dexers will feel the better effects of this. And there's alot less physical eater mods then there are fire. Fire spells are the bulk of a mages damage and if players equip these items to about 30% fire eater most mages will be casting as if they had -15% SDI with anything fire based. That's a max SDI mage anyways and they won't be able to stack SDI to balance out there damage to normal like you'd be able to with HCI/HLA,and DCI/HLD.
Lets see...
Two Non-meddable Armor pieces: Basilisk Hide, Void Infused Kilt. They're the two Damage All Eaters. 1 for gargoyles, 1 for humans.
Humans:
Medable:
20% Kinetic Eater from Lavaliere. Garg/Human.
Non-Med or Non-SC
20% Elemental from Wall of Hungry Mouths.
10% Fire Eater from Jade War Axe (Reasonable PvP weapon)
20% Fire Eater from Draconi's Wrath (but it's a weak PvP weapon)
10% Damage All from Basilisk Hide.
Trade off between shield or potions, but 30% Fire Eater is attainable, 40% maximum.
Mages get up to 20% Kinetic Eater.
So, for humans it seems a bit uneven. Worth noting though, without Mage Armor fighter's regeneration will be terrible. Especially without Mana Leech.
Worth mentioning I tested Kinetic Resonance with a friend and there was still Resonance even against a non-physical damage weapon.
I think it'd be best for an "either/or" effect. Meaning a maximum of 30% Eater, or 18% Damage All, but the effects don't stack. So 20% Fire Eater + 10% Damage Eater would result in 20% Fire, 10% everything else.