Quick question about armor perks (sorry if it's already been asked): Do you need to be wearing a complete set of armor (matching or not) to benefit from a perk? So far, i've been specializing in light armour, and I notice for several of the higher tier perks it says things like "10% chance of avoiding all damage from a melee attack while wearing all Light Armor: head, chest, hands, feet." and "stamina regenerates 50% faster in all Light Armor: head. chest, hands, feet."

Does this mean that if I choose not to wear a hat or a helmet, such perks are completely worthless to me with no benefit at all?

Yes, those that specifically mention 'all xxx armor' kinda need all xxx armor to work.

Off the top of my head, perks that give bonuses to wearing full sets mean you equip the helm, armor, gauntlets and boots. Not wearing the helm negated the perk.

The more advanced ones require you to wear a full suit. So Steel plate helmet, steel plate armor, steel plate guantlets and steel plate boots. Wearing Steel boots instead will cancel the perk.

Well that's kind of stupid. Perk bonuses should work on a per item basis.

Great. So the top three perks of the Light Armor tree are essentially worthless to me. Glad I asked before spending the perk points.