Hey guys, just a heads up, this is still a fine card.
I have a hard time spending XP on purely defensive cards, but in terms of sheer HP tank value you can get in a single action Bulletproof Vest is undisputed champion.
Many powerful heals require 2+ actions, First Aid for example which gives Bulletproof stiff competition takes 5 actions to get full use out of (and is limited). Bulletproof is 1 action for a whopping 4 more health to work with, there is no other card in the game that nets you so much health in so little time.
The action efficiency is important, lots of characters scramble for actions. In solo, actions are your most precious resource. If you're trying to multitask clues and combat in a team, you definitely don't have actions to spare! In a team where you're the key performer in a particular role (the only killer, the only cluer). Bulletproof Vest is a go-to card for the characters who have health trouble but no actions to spare.
Obviously the exact same is true for Elder Sign Amulet and horror.
Leather Coat costs 2 less resources and prevents 2 less pain, I don't see either card as being better, being free makes the card better in certain decks, worse in other decks.
The only card that completely overwhelms the Vest is Deny Existence, where preventing any trigger of 2 damage effectively nets you as much tanking as the Vest would but for 0 actions and no cost while also being there if you have trouble with other stuff.