How much hit % do I need to never miss yellow attacks (Sinister Strike/Backstab/etc.) vs raid bosses (level 63 mobs)?
300 Weapon Skill: 9%
305 Weapon Skill: 6%
315 Weapon Skill: 5% (but you generally should not aim for 315+ Weapon Skill)
This is total hit % required, so if you are playing a regular Combat raiding spec with 5/5 Precision and 2/2 Weapon Expertise, you will not miss yellow attacks (on level 63 mobs) with just 1% hit from gear.