From one point of view, what you say is correct.
I was thinking "artifact" in terms of ultimate cosmic power, manufactured by the gods, pivotal in the destiny of the cosmos, etc, etc.
My advice was meant to keep it out of that high a level of category. Most of my games don't have anything called a "minor" artifact, hence my suggestion.
Unique item, lore and back ground, mysterious aura/abilities. ARTIFACT? No... Artifact (as you described) maybe...why not?
Well, the "Why?" is because that is explicitly what artifacts
are in 4E. One of the neat little modifications made in 4E, to my mind, was the removal of the naff definition of artifacts as "level 10 spells, but for magic items". 4E has a simple, functional and most importantly
useful definition of an artifact as an item tied into the game world, the background and the game situation rather than a player resource for character expansion (possibly earned through adventure).
This makes so much more sense than the "same as magic items, but uber" non-definition that we had earlier that I find myself just facepalming that it's being regressed (and that the regression started with Essentials, in point of fact)...
So, my answer to your second point - there is no such thing as a "minor" artifact. An item with magical or special powers in 4E is either a levelled magic item, designed and intended by the DM as a player group resource, or is a unique and DM-controlled entity that is designed to fulfill some specific role in the game situation being played out, and/or to relate to the game world in a specific way. The latter is an artifact - regardless of its "power level", which is pretty much incidental, in any case (as it's not a character power-up under player control).
Edit: sorry to pick on you - it's not meant as criticism since many seem to have misread 4E the same way, including the designers of Essentials! I'm just bummed at what seemed like a really good idea that has been left to wither on the vine...