Mage Hit Rating (WoW)

The hit rating for raid bosses (skull bosses) is 17%

17% - 446 hit rating
14% - 368 hit rating
11% - 289 hit rating
8% - 210 hit rating

1% of Hit is equal to 26.232 hit rating

Theoretically
Arcane-Frost mages need 11% hit rating since they get 6% from Arcane Focus + Precision
FrostFire mages need 14% hit rating since they get 3% from Precision

Take in consideration that your hit rating can be higher if your raid team has a ShadowPriest or Druid