Although 3 experience is pretty steep for a one-off attack, there are a couple investigators for whom this haymaker plugs a gap.

Carolyn Fern has lots of conditional ways to deal with enemies; her Mind over Matter is best with an otherwise-underwhelming Machete, Shrivelling needs several boosts to be reliable, "I've got a plan!" requires setup, Dynamite Blast is expensive, and Guard Dog or Beat Cop take the ally slot that she would prefer to be Peter Sylvestre. This ranks highly in that company, the self-damage being analogous to dynamite and it can be soaked or healed by usual tricks.

Likewise Marie Lambeau might find this a reasonable addition to her spell arsenal, especially since the damage can off a David Renfield to a doom-free grave.

Its worth pointing out that Leo Anderson has 4 and can take damage with low risk, but he has so many options for dealing with Poltergeist that he can safely ignore it.

Just realise that the wording of parallel Agnes Baker provide an opportunity to "pay" one more damage as an additionnal cost. It can provide an other leverage to make it a 0 cost spell and enlarge the scope to make it a 5 dmg card. Not game breaking but quite fun ;-)

I haven't had a chance to use this card yet, and generally higher-level events are a smaller priority for me in deckbuilding since I tend to focus experience points on assets.

However, I can see people using this card as "Brother Xavier's Parting Gift" - you can play this card and take 3 damage on Brother Xavier for a potential 6 damage on an enemy. That's a powerful attack.

Still, it's something that requires 4 experience, 6 resources, and a few turns of setup in order to do. Is it worth it? Maybe in some situations, but I think usually experience is better invested elsewhere.