How much Block Rating is useful on gear? That’s a question a reader asked me as he began to look at the new gear from Ulduar and from the new Emblems of Conquest vendor much of which is loaded with Block Rating.
Block Rating is the easiest and most efficient way to get to what is called the Block Cap, or what used to be called Uncrushable at Level 70 before Crushing Blows were changed
The Block Cap is a combined Miss, Parry, Dodge, and Block Rating of 102.5%.
Once you reach that point, any additional Block Rating is not helping you.
Oh, it’s still calculated into your Block percentage, but because of the way the attack table works, once you have more than 100% of combined Miss, Parry, Dodge and Block Rating, the game engine (which is what decides what happens in WoW) will not count it. . If you need a refresher on the Attack Table and how it works, I recommend Winchester’s Maintankadin 101 guide.
“Picture it like a table, and there is only room for 100 plates on the table. 1% stands for 1 plate, you arrange the plates from left to right. When you're Block Capped you've basically just pushed the "hit" plates off the table to make room for the avoidance ones, because they have a higher priority.”
You are 'capped' on the amount of Block you can have. It should be noted that since Holy Shield was changed to have its duration be longer than it’s cooldown, it is now safe to assume 100% uptime on Holy Shield when calculating your Block Cap.
When this happens, you should start replacing Block with other avoidances (namely Dodge and Parry).
Being at the Block Cap is very helpful because it means that every unavoided attack from the Boss will be a Block. Paladins are probably the easiest tank class to keep Block Capped 100% of the time.
Each Block takes off damage equal to your Block Value. If the Boss hits for 15,000, and you have 1500 Block Value (not unreasonable), you effectively shave off 10% of the damage each and every hit that isn’t outright avoided. That can add up to a huge amount of damage reduction over the course of the fight. Our last battle with Kologarn, I blocked 12 times and saved myself from tanking over 23,000 damage, which works out to rougly a 6.6% damage reduction over the course of the fight.
To reiterate, because it doesn’t suffer from Dimishing Returns, Block Rating is the fastest, easiest, most efficient way to get Block Capped, but once you are there it looses its appeal completely and becomes useless.
So is all the Block Rating on the new Ulduar/Emblem gear good? It depends on your current gear and how the upgrade will affect you.
I would suggest that the Developers should examine combining Block Rating and Block Value into a single stat called Block. That would allow Block to remain useful regardless of if you are over the Block Cap or not, and remove the confusion between Block Value and Block Rating.