If am right, your chance to attack have soo much things, to choose, you hit or no. Your agi, wep-skill, attack, fatigue (and maybe more) AND, your enemy agi, fatigue, armorskill.
And ye this is qute annoying
, but this like an (RPG) dice, when you hit attack, ya throw the dice.
And after all, the good build, like (orc, main wep skill two-h-axe, main att, str+agi, +warrior born), you basically must have 60%+ hit chance.