Guides: Karazhan, Zul'Aman
WoW-math: All about +Hit/Expertise Rating, Armor Penetration calculations, Combat table generator

This webpage will generate your combat table for Yellow and White attacks. With this you can see what your crit-cap is.
I also assume you attack from behind, so no Block or Parry is involved.
You're a lvl 70 Player and your target is a lvl 73/Boss.

Hit%
Crit%
Expertise%

Dual Wielding