I'm really concerned with the value listed (or lack thereof) for Block rating. If you had a choice between 30 dodge rating and 18 Block rating, what do you choose? Avoidance wise, the 18 Block rating counts for more.
Then, you have the issue of not taking into consideration the other gear supporting it. What if that minor difference pushed you into the avoidance cap? Would the dodge still be better just because it's valued better. Personally I'd rather know that I'm over the block cap rather than being under it with slightly less raw avoidance.
Concerning Block Value (This is based on the assumption that you are Block-capped). Your block stops 200+ BV(items)+ BV(shield)+ BV(str) damage. The idea is that each attack based on RNG overtime will produce that amount of damage less than normal if blocked. So, If you have someone with 50% raw avoidance and 1000 BV, and another with 46% raw avoidance and 1100 BV - which receives less damage?
When taking an average of 8000 damage per hit, they will be the same. If the damage increases, the person with the block value begins to take more damage overall and would need more avoidance to equal out (at 9k damage they would need 47%). On the same token, taking less damage per hit (4k), With that amount of BV you would only need to have 40% avoidance to equal out the damage taken overall.
I'm not a mathematician so my numbers could be a bit off - That's just a rough way to explain how BV does have a distinct correlation to EH and overall tanking ability. Yes, there are ways of quantifying BV - I'm not really sure how you would overall.
TL;DR - Block Rating needs to be counted for tank points - Block Value is quantifiable and directly effects tanking ability - Items should be considered in the set, not individually counted for points.
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Aleyona of
Srs Bsns