The first thing that needs to be clarified is that there are two Block values of importance.
- Block chance, i.e. how likely are you able to block the incoming attack.
- Block amount, i.e. when you successfully block, how much of the incoming attack’s damage is mitigated
I’ll use my Invoker as an example…
As you can see, her base Block Chance is 31%. In combat, that will rise (due to abilities) and whilst the in-game tooltip says this chance caps out at 75%, that’s not actually true. You can actually get Block Chance to be over 100% with the right combination of skills / runes / gear / cubing. However, that’s just deciding whether she successfully blocks or not…
Assuming she blocks, that’s when the Block Amount comes into play. That’s how much of an incoming attack’s damage is mitigated / ignored. So, say a mob was going to hit me for 500K damage. With a Block Amount of 25.0-32.8K, the incoming damage would be reduced to 467.2-475K when the Block was successful.
Even if you get Block Chance to 100%, you’ll never get Block Amount high enough to mitigate a lot of damage. That’s why you need stuff like Armour (from gear and STR) and All Resist (from gear and INT) and defensive items such as Justice Lantern, Aquila Cuirass, and so on, and why shields / weapons tend to be picked for their offensive legendary abilities, not their blocking chance.