The Worgen racial Viciousness provides 1% crit. Will this stack before or after gear? As in will it ALWAYS provide 1% crit no matter my gear, or will it be subject to any kind of Diminishing returns?
Critical strike chance does not suffer any form of diminishing returns. While some melee classes can, at extreme (Read:highly unlikely to be reached in Cataclysm) gear levels, this is a hard cap, not a point of DR.
Similarly, while there is a flat reduction in your chance to critically hit a raid boss, this is a flat reduction. Not DR. Every additional point of crit rating or +1% to crit increases your chance to crit by as much as the last point did until you reach 100% (or the aforementioned melee cap.)
Viciousness stacks with everything, and stacks additively.