Totem of Wrath debuffs the mob, increasing the chance it will be critically hit by 3%. This stacks with every other crit enhancer in the game. The shaman ability which is inferior to the druid version, and will not stack with the druid crit increase is Elemental Oath, which increases crit chance for 15 seconds after the shaman has a critical hit.

Gear will come as you level up. If you don't have a lot of BC level gear, then the Wrath level gear will be that much of an increase immediately. I believe the first quest reward, maybe 3rd quest in the initial quest chain, was a spell damage weapon comparable to the the Kara Prince / Gruul caster weapon.