As an archer, your attack speed is not as fast as sword or dagger so the better chance to critical hit the better for your survival against swarming or tough enemies. If you can create or fine 4 fortify archery items and wear them all you will see that critical is very useful for in-combat (not while sneaking around). My best one for now is Ebony Bow enchanted with shock (25dmg) with full options for pure archery (currently) Ebony bow of mine deal about 110 dmg (x3 sneaky critical) > 330+25 quite hard eh?

while in-combat still hit hard with 1/5 chance to critical.