Enchanted Blade(3) is truly one-of-a-kind. Its charges are never wasted, since you would only use a charge if you succeed the test. Card drawing and horror healing off defeated enemies are amazing. Having the flexibility to deal 1 damage on demand is nice. However 3 charges are simply not enough as a primary damage source, and it is better to save the charges for finishing blows anyway. I think the blade is ok-ish on its own, but amazing if you have an alternative damage source.
Pairing the blade with other melee weapons, i.e. Machete or Timeworn Brand, serves two purposes: 1. Temporary damage source and card draw before you draw the main hand weapon, and 2. efficient horror healing afterwards. This pairing is particularly good for Mark Harrigan (and to some extent Roland Banks), who can utilize the horror healing and relatively low boost well.
Pairing the blade with a big gun serves a third purpose, which is to kill 1-2 health enemies which would otherwise waste precious ammos of the big gun. This however requires Bandolier (or its upgraded version), which together with the big gun itself, requires quite a setup. This pairing works best in a deck with good economy.
There is a pairing I found particularly interesting: With Agency Backup. Agency Backup is really good for providing stream of constant damage (and testless clues), but when it comes to monster killing it is the burst that matters. The blade compliments it really well. Tab Agency Backup once (or more with Charisma and/or Mitch Brown), then finish with the blade would be a splendid way to kill a 3-4 health enemy. The blade is also not too expensive to play alongside Agency Backup. If you ever want to try to build a deck centered around Agency Backup, Beat Cop(2) and ally-buffing cards, I believe Enchanted Blade(3) is the weapon of choice.
Side note: Don't pair the blade with Double or Nothing. The "spend 1 charge to..." phrase is part of the "if you succeed..." effect, so you still need to spend 2 charges to deal 4 damage. Also only either the first time or the second time of resolving defeats the enemy but not both, so you still only get to heal horror and draw card once.