Okay! Thanks for the feedback! What kind of indicators could I add to make it more clear next time?
It's hard to say for sure, but it feels like the player character's attack hitboxes are smaller than the slash animation and that leads to attacks missing when they look like they should have hit. For the goblins specifically, I think their attacks either have too much reach or come out too quickly. Making sure that the hitboxes are closely following the weapon sprites should help the attacks feel more fair and avoidable overall.