Less Block Chance - no difference?

Why does 4% less Spell Bock not change my max Hit/EHP?
Goes down from 88 to 84%

Not according to PoB.

Sorry, i dont understand it.
Isnt more block always better untill its capped?

Yes, luck rolls can reach the cap sometimes but not always.

Yes, I agree with the above. Block is unrelated to max hit, because blocking prevents all the damage, but does not lower the damage taken when you are hit. The only case where this may be different, is if you are taking a portion of the damage, like from Glancing blows. However, even with Glancing blows, max hit will be occurring on the hits where you are not blocking. So glancing blows would effect the max hit on hits you block, but the max hit overall will be on hits you don't block. Increasing the percentage of time you block does not alter the amount of damage taken when you do not block. The same thing can be seen for spell suppression on max hit for spell damage. Having 99% spell suppression will not change the max hit values, because the max hit will be occurring on the 1% of time that you do not suppress. If you get it to 100% suppress, the max hit will double (by default) because there is never a case where the spell damage is not being suppress.

For EHP it is related. In your first image it is saying that you have 88% spell block and it is over capped by 7%. In the second image you have 84% spell block and it is indicating that max spell block is not being exceeded.

This should lower the EHP that is based on spell block. You are not showing an image of the EHP changing/not changing, but as you are saying it does not change, and showing that it is not indicating there to be no change on the mastery mouse over, I assume that the value is not changing. I am replicating something similar in POB, where just the spell block is dipping below max. As expected, EHP does drop. One possible reason for why it may not be dropping on your POB, is the configuration settings. These are taken into account in the EHP calculation. For example, if you have the enemy damage type set to a type of damage that can not be blocked by spell block, spell block will no longer be effecting the EHP calculation and thus changing Spell block would not alter the EHP numbers. To investigate this or any other possible reasons further, having the POB directly would make it easier to see exactly what is causing it.

As pointed out, with versatile combatant POB will be showing lucky block chance statistics on the LHS panel. So these numbers are above, but based upon your actual block/max block numbers. I think it would be useful if POB had an effective value for block and suppression on the panel. A bit like the effective crit chance does for crit, which takes into account luck and accuracy. The base numbers are available though if you want to see them in the calculations tab. There is already a lot of values on this panel, so perhaps the creators are trying to minimise how many values are showing by only listing the most relevant ones.

Thank you Gentlemen.

I wont pretend to fully understand everything but every little bit helps to get a grasp.