I'll compare this to Spectral Razor since they fill many of the same use cases
- Testless damage. Depending on your difficulty this could be very valuable
- Potentially Costs 1 less if you're targeting low health enemies like Acolytes
- Synergy with arcane slot increasing effects such as Familiar Spirit
- Synergy with empty arcane slots, clearing the way for a beefed up Eldritch Initiation
- Anti-synergy with standard arcane slot spells (unless you managed to spend all the charges already)
- Must be engaged. Razor comes with a free engage to deal with pesky aloof enemies
- Increasing the damage potential still requires you to pay one more resource per damage. You can easily reach Dynamite Blast cost but for situationally less payoff since you're always targeting just one enemy.
- Only target non-elite. This a deal breaker.
In my opinion the best reason to run EW over Razor is to lean into that big payoff explosion. This requires you setting up assets to maximize your slot conversion which will be a significant resource and card investment. All of that setup to be able to target basic enemies only is a let down.
For most investigators Razor will get you more mileage. The only Mystics who I can see potentially taking Ward are those who cant reach useful + scores (so just Marie Lambeau?)