POE2. Maps one shot???

I’ve started doing maps now, but it seems they only allow one use. Is this a bug, or is it intended to work this way? Am I missing something that would let me use the usual five attempts?

I tried googling this a little, but I couldn’t find any information on the matter.

I play new 8 charaters and 0 death on story map after i understand little how move roll dodge and aoe radius.
But not understand one shot on maping from boss or on trial if class hawe 3k HP 85% armour and resist 80/80/80/75.
Any boss one shot mi every time hit after roll end and other fun moment.Monkye boss Engenner boss Terracota guard on trial 75+. I dont understand this too.

3k HP is OK but a bit on the low side for high level maps for Titans and Smiths, if you are one of those. You can push it to 3.5k fairly reasonably, even 4k.

The armour equation that describes the amount of damage mitigated by armour is AR / (AR + 10 * incoming_damage).

So, if you have 20 000 armour, and are hit for 500 damage, the damage you receive is:

500 * (1 - 20000 / (20000 + 10 * 500)) = 100. You mitigated 80% of the damage.

If you are hit for 4000 damage, it's:

4000 * (1 - 20000 / (20000 + 10 * 4000)) = 2667. So you only "only" 33% of the damage.

It's generally required to add in some additional mitigation, even if it's only a little. If you can for example take 5% of physical damage as elemental damage, that's worth it. If you can wield a shield with additional %phys damage reduction, that's worth it.

As a rule of thumb, you need 10x the incoming damage in armour to mitigate half of incoming damage with armour.

You also need to max elemental and chaos resistances.