A character can look tough on the sheet and still fold when Torment damage starts landing in quick bursts. That is why D4 items should be judged by the whole defensive picture, not by one armour number. Armour matters, of course. It softens physical hits and gives every class some breathing room. But piling it on after you are already comfortable often costs you life, resistance, speed, or damage. Those losses show up fast when elite packs, boss attacks, and ground effects all arrive at once.
Start with the useful target
For most runs from Torment 1 to Torment 12, around 75 percent armour reduction is a sensible place to stop. It is enough for routine fights, farming sessions, and most dungeon pressure without forcing awkward gear choices. Once you are near that mark, check what is actually killing you. If it is elemental damage, armour will not solve it. If you are getting clipped while moving, more movement speed or a defensive skill may do more work. A practical order looks like this.
Reach roughly 75 percent armour reduction.
Raise elemental resistances to a reliable level.
Build a larger maximum-life pool.
Add mobility, recovery, barriers, or damage reduction where your build supports them.
What each choice gives you
Defence What it helps with When it becomes valuable
Armour Physical hits Before reaching the 75 percent area
Maximum life Large mixed damage bursts At every Torment level
Resistances Fire, cold, lightning, poison, shadow damage Against bosses and dense elite groups
Movement speed Avoiding telegraphed attacks When positioning is the real problem
The table is not a rigid rulebook. Some builds heal constantly, while others rely on barriers or Fortify. Still, the point holds: armour is one part of the job. Extra armour past your useful target brings smaller gains, so each new roll has to earn its slot. A big life roll may save a run where a tiny armour increase changes nothing.
When going higher makes sense
There is one clear exception. If you are pushing the harshest activities and every hit is tuned to hurt, moving closer to 80 percent armour reduction can be worth it. That extra margin may help during a boss phase where dodging is limited or recovery is delayed. Even then, do not strip away your life pool just to reach it. Players often chase a clean-looking defensive number, then wonder why poison pools or elemental bursts still take them out. The answer is usually elsewhere on the character sheet.
Build for the damage you actually take
Use tempering and crafting to fill the gaps your playstyle exposes. If you die while running between packs, add speed or recovery. If a boss removes half your health in one swing, add life and reliable mitigation. If resistance is low, fix that before chasing small armour gains. When you D4 items buy for an upgrade, look for pieces that support several needs at once, then test them in real fights rather than trusting one defensive stat.