One thing to remember about defense is how soon you get it - I have a Redgaurd who wears smitthed heavy armor and uses a 2H weapon (usually a hammer, but I occasionally grab a greatsword). With a sword and board, you presumably getter better defense early in the game. With Heavy Armor and 2H weapon, you can block, but it's not as effective as blocking with a shield - but it does still help once you get some levels and a few perks in the basic blocking perk (the one at the base of the tree which you can upgrade 5 times) in blocking.
Now that I've got Legendary Ebony armor (and am well perked in Heavy Armor), I hardly even bother with blocking anymore - the only thing which really threatens me is magic - weapon attacks mostly just bounce off my armor - including arrows.
So, as far as I know, it breaks down sort of along these lines:
1h + shield + armor - low damage early, moderate damage later, high defense early
2h + armor - moderate damage, moderate defense early, high defense later
dual 1h + armor - high damage, low defense early, high defense later
dual 1h + light armor - very high damage (more stamina; more power attacks) early, very low defense early, moderate defense later