[renowner]

So I just did some napkin math for this. The actual effect the torso has isn't very intuitive because it's a flat modifier to a multiplicative damage source; ie, it's not purely 25% DR against low-power crits.

The formula for critical damage is essentially base damage multiplied by the critical rate, or D(1+0.01x), where D is the damage before crits and x is the critical modifier. The formula for critical damage reduced by the torso is D(1+0.01(x-25)). With fancy math shenanigans, we can divide the new damage by the old damage, reduce it, and come up with something that looks like y=(0.75+0.01x)/(1.00+0.01x) to see how much effective damage resistance this item gives based on the user's effective critical damage.

You can even graph it if you want, but effectively, at 50% critical damage, you receive 16.7% DR. At 100% critical damage, like daggers can easily achieve, you would receive 12.5% DR against crits. Powerful and useful, but still situational and even in those situations, not gamebreaking like this thread would lead you to believe.

In short, stop kneejerking about new items actually being potentially useful before even seeing how they affect the game.

First of all, nobody said that its a free -25% damage to all crits forever. That'd be beyond stupid. 
Second of all, even if we assume its going to be an average of -15% damage taken from all dagger crits, and around 20% less damage taken from some spear and sword and handgun crits, and some bows  (More from fists but i've not seen a fist crit build in so long) . . . That on its own is probably fair. However.

As we noted. It also gives +25 hp. +25 fp. And has extremely low weight and rarity.

Nobody said it was the most broken thing ever. Nobody said it was horrifically overpowered. What we're saying is that its doing too much too easily and basically has become the new terrasque shell auto include to just about everyone using heavy armor. Terrasque shell being a nine star. This being a six star. And this is definitely stronger than terrasque shell against crit builds with lower base power weapons. By a huge margin. And only slightly weaker than terrasque shell otherwise.(I value FP more than Hp boosts on equipment, but Terrasque does give a tiny bit of hp regen which adds up over time.) They have roughly the same weight.  Its also about as good as bodyguard, except at half the weight.

It should get a slight nerf. 
Or other heavy armor should get a slight buff. Most of them are trash.