You forget that block is EH if you are at the block cap and can keep HS up all the time. It only becomes EH when you are block capped because only then can you be 100% sure you won't get a bad string where all the hits go through. It's like the reason you don't put dodge into your EH calculations, except with block you can get to the point that you can include it.
If the boss is hitting for 10k, and I'm blocking 1.5k of each attack, that's 15% less damage taken. That's about 17% more EH. With 30k health that would be equivalent to about 5k health. Is not being blocked capped getting you 5k health? That would be quite the feat. And that's a fight with a 10k hitter. If those hits were only 6k you'd have over 30% more health.
Getting blocked cap is the best investment you can make towards your EH
for physical damage.
Magic damage conveniently ignores block.

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No really, I'm not
addicted.