My first thought viewing this card was: When would I play this? As it doesn't help protect me during Mythos and it really doesn't help with fighting tough enemies since if I'm already comfortable passing attack tests against an enemy why would I commit it later?
The answer is you should view this card as opposite Take the Initiative in which you commit it on predominately non-Mythos/fight actions after smoking an enemy. On average you can expect to do two attacks for a round, that means when you commit it anytime to a valid skill test for the rest of that round that performing investigator gets +3 on it or +6 fight if they plan on punching anything. Seeker sad you had to deal with an enemy instead of a Locked Door at the same location? Well now they can get +6 for it.
But we can go further as you can successfully attack 3+ times with things like One-Two Punch, Leo De Luca, Luger P08, Lily's Agility Discipline, or Remington Model 1858. More attacks mean you can easily end up with a skill card on par with Promise of Power or Last Chance. Furthermore, if you decide to pick-up Bestow Resolve you can let anyone nearby blow any skill test out of the water by doubling the wild icons.
Granting someone +3/+4 on a skill test after pummeling enemies is pretty good and even if you don't have a teammate nearby you will likely want to commit it to Guardian's favorite encounter card Frozen in Fear, other nasty in your threat area tests, and/or location tests. Which you often want to do after smashing an enemy to dust to not take AOOs.
The only sad thing is that this card is not Practiced for folks like Mark/Roland (likely due to Amanda/PMP). Because if it was, I could see this easily becoming a staple alternative to Take the Initiative in which you trade Mythos protection for a more powerful investigator phase card.
As for now it's a solid lvl 0 card geared towards those who can get additional attacks off and don't need as much encounter protection as it does have its bad moments where you need to commit worse Unexpected Courage to hopefully pass a deadly test before you can fight and/or you miss all your attacks.