Guys, a 2 dot artifact can mimic a essence 2 charm.
Does that mean a 2 dot artifact can give you a perfect defense?
Okay so, here is the component you are missing, the "Can," which is the part where the Artifact version of a given effect has a lot more baggage involved than the Charm-equivalent does. Mostly because these are two dissimilar chunks of mechanics trying to do the same things in redundantly overlapping ways.
First point, Perfect defenses aren't typically entry-level access powers, they usually require some kind of XP buy-in that establishes that there was an Investment Paid into having that perfect defense in the first place. Charms have trees, creating an escalating XP path, where any given effect must be judged by how many prerequisite Charms you need to buy to reach it. Before Evocations deliberately chose to blur that line, there's nothing to point to a comparable payment requirement (as Artifacts are, at best, by houserule, a Rating x3 xp jump between dot-ratings, which barely fits average XP costs to dip into a tree), so it was safe to conclude that anything of a given threshold further than one Charm-purchase away is off-limits for the wide variety of Artifacts.
Second, is the part where the Artifact usually has some other, non-Charm-emulating function by nature of being a physical object. A sword with a built-in Excellency is still a sword, foremost. Which means that you have to mentally attach that benefit Also onto the Charm it is emulating. Its not simply an Excellency-sword anymore, but approached as an Excellency which allows you to deal and parry Lethal Damage with a 'conjured' weapon statline, a non-unarmed attack, the whole nine yards. This means that there is no standalone "this trinket is a Charm in physical form" Artifacts, because they simply cannot exist, because once you start applying the natural benefits of that Artifact onto the Charmlike effect, even simply to the degree of "I can unattune this, and hand it to someone else to attune and use instead" you get a Vastly higher Essence minimum than you started with.
Third, tying together the first two points, a suitable Artifact to be judging an effect against is not actually emulating a spot-fire instant-use Charm like a Perfect, but a
Scenelong Charm with a "mote payment" extra clause owing to the commitment of Essence simply to hold Access to that ability in the first place. An Artifact with a magic power is gating access to that power behind its mechanics as a magic object, and so has more in common with Solar Hero Form than it does anything else, and that's before you start adjusting costs for not being an intangible magic-exception to the rules. Would you fairly eyeball anything which grants an innate Perfect defense trigger by Essence 2 as a scenelong benefit, as an entry-level power? Even if it included a binary Y/N conditional switch to activate like that of a "have you been disarmed of this" artifact? Not many people would.
So no, trying to draw a 1:1 correlation between the two for having similar numbers attached is optimistic at best, and the ticket to bad homebrew at worst.