Shield Block Increases Block by 75% until 1 blocked attack occurs on use of base ability of warrior , can only be used while in defensive stance.
The Improved Shield Block talent of protection tree adds 1 extra block and duration for + .5 seconds every talent point , for up to a total of 4 blocks and 6.5 seconds can be achieved from 3/3 improved shield block.
This talent is highly important for an endgame tanking Warrior. According to combat parsing, it's been more or less proven that achieving very high block rates pushes crushing blows off of the combat table. (See .) And this talent effectively doubles the number of hits that will be blocked. Spamming Shield Block with this talent means that almost all attacks will be misses, dodges, parries, or blocks, except with very low attack speed mobs.