The Eater property can be both weak and powerful.
On one hand it doesn't stop you taking damage. On the other hand it restores a small % of the damage you do take.
So at 70 resist of any damage type, you effectively take 30% damage.
If you max your damage eater out in that damage type you'd be restoring 30% of that damage taken. Which is about 9% of the initial damage dealt.
This is like a delayed 79 resist.
This effectively allows players to exceed the resists cap and take less damage.
Initially where there were fewer items available with these properties, it was much harder for players to pile them on. As more items enter the game with these properties, the ease of achieving the max eater% will go up. As well as the more widespread usefulness of the items the properties are on.
Of course ongoing balancing may find that they need to be beefed up a little or toned down, have to see where the game grows.