There's been a bit of discussion recently about how to spec, gem, and gear come 3.0 and WotLK. To add to that discussion, it might help to look at our damage reduction with the upcoming changes to tanking mechanics for Protection Warriors.
Over the length of a boss fight, there will be an average damage output by a boss. The actual output of that average dps at any given time will include spikes and lulls in the output due to strings of misses, strings of hits, special attacks, etc. In dealing with that damage, there are two types of damage reduction to consider:
1) Spiked damage reduction -- The incoming damage is completely avoided or mostly mitigated.
2) Consistent damage reduction -- The general mitigation to the raw damage of incoming attacks
3.0/WotLK will have our usual spike damage reduction from misses, parries, and dodges. The one new inclusion that has been added are critical blocks. Fully talented, the Critical Block talent will double the amount of mitigation from blocking on 30% of blocked attacks. With SBV values increasing significantly in 3.0/WotLK it would not be unlikely to see critical blocks providing full mitigation to some attacks.
Shield wall is now less effective, but can be used more frequently. Fully talented Improved Spell Reflection will also reduce the chance that you'll be hit by (ie. completely avoid) a spell by 4%.
The Shield Specialization talent grants 5% increased chance to block attacks (also generates 2 rage per block). Given critical blocks, this will feed into the rate of spiked damage reduction.
The new Shockwave talent will provide a 4 second stun to all mobs in its AOE cone. I'm not counting on this effecting raid bosses, but it will give some very useful spiked damage reduction to an unlimited number of targets.
The Shield Block ability will now only be usable once every 40 seconds when talented, however, it will increase SBV and chance to block by 100% for 10 seconds. Combined with a few critical blocks, this will produce periods of significant damage reduction.
Of other worthwhile mention for spiked damage reduction, a Protection Warrior OT can make some situational use out of Vigilance on the MT for the 3% damage reduction when threat levels permit. Safeguard is another worthwhile talent to note, as a Protection Warrior OT will be able to reduce incoming damage to the MT by 30% for 6 second periods by intervening.
Consistent damage reduction will have the usual influence due to armor from improved gear which will continue to get a 10% increase from the Toughness talent. This really is the bread-and-butter of what keeps incoming damage survivable. However, we now have a much more prominent role of SBV in providing consistent damage reduction.
Gear is being allocated a lot more strength and the strength to SBV ratio is now 2:1. To improve reduced damage due to blocked attacks we have the following related talents:
Shield Mastery - Increase SBV by 30% and reduce the CD of Shield Block by 20 seconds.
Vitality - The 6% increase to STR feeds directly into SBV
Overall, we'll have some familiar spiked and consistent damage reduction mechanisms in the game. Our new game mechanics should make tanking, whether grinding, instancing, or raiding, fresh and exciting. 3.0/WotLK will in a number of ways be a new game for Protection Warriors to enjoy.