Death Knight(DK) Caps
The 1 weapon(a 2-handed weapon) death knight hit cap is 8% or 262 (this is the cap you want to reach first)
dual wield hit cap is 27% (yes this is an insane amount)
Death knight spell hit cap is 17% or 446(effects Icy Touch, Howling Blast, Death Coil and Pestilence)(Virulence and Misery are worth 79 Hit each they they can do a lot towards hitting your cap)
Death knight Expertise cap is 6.5% for DPS and 15% for tanks.
Death Knight Tanking Caps:
Dodge cap is 88%
DK Parry cap is 47%
Miss cap is 16%
DK Defense skill needed to be uncritibal by bosses in raids is 540
Spell power does not effect any death knight spell so do not ever wear gear with spell power on it.
This information is current to 3.0.8.