Here is a tanking Crusader build: Fire Wall
http://us.battle.net/d3/en/calculator/crusader#aZSdfi!YUhV!acZcYa
This build raises all defenses and punishes those who want to pass through them. With this spec, the Block is like its Hot (block 100,000 damage in 10 seconds) achievement popped on the 1st group of mobs (at level 64) within about 3-5 sec (had a level 60 shield so it only stopped a maximum of about 4,000 per hit). The best part, is right when that achievement popped, all of the enemies were dead, due to Punish-Roar. This causes all blocks to deal 45% weapon damage as fire to all enemies within 15 yards.
This is one of the main AoE damage methods of this build, but it has several more tricks up its sleeve. Whether enemies are up close and personal or are a fair distance away, and group of enemies fall quickly to Blessed Shield-Combust, due to its 33% chance to cause a fiery explosion on its original target and its 3 ricochet victims. Plus, if you have recently hit something (doesn’t have to be an enemy) your Punish effect increases your block chance, which further increases the damage of your Blessed Shield. Then, if you want to close the gap between you and that group, or just have a single target, Shield Bash will be your next choice skill (which also gains more damage from having an increased block chance) since it deals 550% weapon damage.