chardev.org - a World of Warcraft Character Planner - x
About 90% coverage from gear + 5% from mob base miss, rest is covered by raid buffs. (typically you can't get 102.4% unless you had like insect swarm/scorpid up on the mob, so anything without those up you're close to capped)
At 97~% coverage you're still blocking just about everything!
And the +9900 is added to their base swing, which means it still has to go through armor, then finally block value. Block is calculated at the very end of all attacks, even after shield wall