Since all the other caster forums is failing at this, I might as well write a little quick post about it.
The required amount of hit against a raidboss is 17% - This applies to ALL spells.
17% spellhit is 214 hit rating at level 70 !
We get 3% + 3% = 6% from talents.
11% spellhit is 139 hit rating at level 70 !
You'll need 139 hit rating on your gear for level 70 raiding