11/09/2011 08:42 PMWhy the shift?
Posted by Tanker
I'll try to give some insight into how things got to where they are now.
Originally, things were much different. Block was a static value. This presented much of the same problems as Blood has with Blood Shield these days - it worked really well against trivial damage, and not so well against more severe damage.
As a mitigation stat, Block was largely ignorable against raid bosses - the amount of damage blocked was that insignificant. It had value, though, in that it prevented Crushing Blows which hit for 1.5x damage. The necessity of block capping before Wrath wasn't because Block was some amazing mitigation tool, it was because being Crushed was deadly. You cared that you blocked, but not how much.
Things changed in Wrath. Crushing Blows went away - they could (and as of yet, still can) only occur if an opponent 4 or more levels above you is hitting you. This simplified tank balance, since with the introduction of DKs, there were now two non-block tanks. However, static value block still caused issues. As a stat for raid tanks, it was terrible with a couple exceptions where it was fantastic. (Against Icehowl? Terrible. Against Anub'arak adds? Fantastic.)
Things changed again in Cata. Block became a percentage effect. This solved the scaling issues, and let tanks gear more uniformly for everything. Unfortunately, even after all these tweaks over the years, block is still causing trouble.
The trouble now is that block capping gives you constant 30% (minimum) DR against melee attacks. Druids and DKs look bad by comparison, since they're still capable of taking full hits (Xayton Punches). Against any boss that really stresses tank survivability through melee damage, block capping is a gigantic advantage.
Now, calling block OP because it can be capped is a bit misleading. Mathematically, you get about the same total damage reduction from an equivalent amount of dodge or parry. In a hypothetical scenario that doesn't unfairly favor one form of tank mastery over another, they'll mitigate approximately equivalent amounts of damage.
It's specifically the fact that block tanks can gear to never take a full hit that makes the current situation a problem. It's extra stress for the encounter design team, because they have to work harder to avoid making bosses that can only be tanked by block tanks. It's extra stress for the class balance folks, because they've had to keep tweaking non-block tank mitigation upwards so that they don't compare badly. And it's not that great for players, because of class favoritism.
Basically, block capping is too much of a good thing.