Please don't take this card without talking to your teammates first. Sure, it sounds like a clutch card, but in practice, keep in mind:
1.) you have to OVERsucceed to get literally any use from this card whatsoever. and even if you do manage that against monsters with high fight, you aren't reducing the fight value by much. I'm going to guess an average of 1-2.
2.) This only lasts for one attack. ONE attack. Unless your teammate is close by and also using a Shotgun, a (well-used) Double or Nothing, etc. that can abuse the heck out of an easy fight test, you're just getting a mildly easier attack.
On top of that, you as a Seeker are spending an XP and card slot on something that isn't at all conducive to seeking (clues, cards) or self-defense. Trust me, there are much better cards for Seeker self-defense that DON'T cost 1 XP. Yea, cool, you reduced some enemy's fight value from 3 to 0 for one punch, but if your combat-oriented teammates desperately and frequently needed something like that, chances are what they really needed is to build their investigators to be more consistent. Spend your XP on something that will make you better at YOUR job (or, again, something to pull your own butt out of the fire).
Maybe this card does have its place, but you (and more specifically, your team) really need to have something worthwhile built around it. This card fills a pretty specific combat-support niche, and if you undershoot that, you're going to be disappointed. In my personal opinion, the setup that your team needs to intentionally make this card worth it.....is not worth it. I can visualize a few different, down-to-the-wire scenarios where a well-placed Expose Weakness (with a VERY forgiving chaos bag) could win you the game, but I'm not willing to shovel my money into a losing slot machine in the hopes of that triple 7.
tl;dr: yes for someone, no for me