Melee

​What factors effect my likelihood of hitting in melee?

Your attack skill
Target defence skill
Being surrounded (Huge bonus if target is surrounded, a much smaller penalty if the attacker is surrounded)
Being injured (Similar penalty to both attacker and target)
Being fatigued (Similar penalty to both attacker and target) 
Being afraid (Similar penalty to both attacker and target)

Having a shield
Being in Defensive mode

Skills, poisoning, traits - too many to mention in detail!