DK Tank expertise and hit requirements

[Stealthy]

Both Hit and Expertise help generate threat.

33 Hit Rating = 1% increased chance to hit
33 Expertise Rating = 4 Expertise Skill = 1% reduced chance for mob to block or parry

26 Expertise skill eliminates the chance for a boss mob to dodge (soft Expertise cap)
57 Expertise skill eliminates the chance for a boss mob to parry (hard Expertise cap)

Having enough effective health and avoidance for a boss fight is usually the priority, threat is the next thing to focus on - but you can't just stack one and not worry about the other.

Cheers,
S.