Aim for 5% hit. As far as I know, any higher will be wasted most of the time. You may notice missing Melee more based on some % based damage mitigation that works through misses - these cannot be negated.
Expertise and Spell Penetration are there only to overcome your opponent's defenses - so it will greatly depend on their class/spec/buffs. I would not consider them a wasted secondary stat, but it's also highly situational (moreso than, say, Crit or Haste.)
As always, Resilience's smoothing-over of damage intake is still regarded as top dog.
Edited, Jan 8th 2011 3:32am by tzsjynx