
The level 0 Enchanted Blade is a staple that sees play as a two-of in the vast majority of Guardian decks at my table. You can tell the designers worked hard to make sure this upgrade would have special appeal to Guardian players. Everyone knows that Guardians are a bit soft to horror and (Soldiers excepted) a bit short on card draw. This card addresses both issues. And everyone knows how bad it feels to spend ammo only to draw the autofail and miss. That will never happen with this upgrade. Plus, this card is just cool.
All that said, this card basically never sees play in my group. Why is that? Well, the main problem with Enchanted Blade is that it's a mid-tier weapon, and that's a really awkward spot to be in this game. Think of it this way. If you're a Guardian playing the classic Guardian role of protecting your teammates and hunting down monsters, your weapon is very likely the most important card in your deck. It's going to have the biggest impact of any card in your deck on the effectiveness of your Fight actions--and those actions are what makes or breaks your success as a character.
So, when you're shopping for weapons, why would you settle for anything but the best? It makes so much more sense to save up a bit and get the truly amazing weapons, like the Flamethrower or the Lightning Gun. The extra damage and to-hit granted by those weapons just does so much to make your character stronger. Enchanted Blade dealing a measly 2 damage per action (and that at most 3 times) just can't hold a candle to the power of the 5 XP weapons. And, once you have your superweapons, it just doesn't make much sense to spend 3-6 XP on what would basically be a sidearm or a backup weapon. If you have Enchanted Blade and Flamethrower in your deck, and draw them both, Enchanted Blade will probably do literally nothing for you that scenario. That's not a good return on an XP card. It would be much better to spend XP on cards that would complement your superweapon, like Stick to the Plan or Stand Together or Custom Ammunition or what have you.
And yes, I'm aware that Bandolier exists. But if you already have one super-great weapon in play, do you really need to spend a lot of resources and XP to get a worse weapon in play to go alongside that? Probably not.
Enchanted Blade is not the only card to fall victim to this complex. The upgraded Blackjack and the Taboo'd Machete face similar issues. It's not that these are weak cards--Machete was famously dominant back when it cost 0 XP. But they're not as strong as other options for your primary weapon, and people usually aren't willing to spend XP on backups.
That leaves Enchanted Blade with only a very small niche. It is one-handed, so if for some reason you really, really need that extra hand slot (perhaps you're a solo Guardian who wants a Flashlight but is allergic to the Timeworn Brand), you can justify it. But in multiplayer, for the focused Guardian, this card just isn't really up to the task.