A displayed armour rating of 567 will cap at 80%. The displayed armour rating is dependent on several factors (base armour rating + shield rating + armour effects)
So if you find you are absorbing too much damage, look for a displayed rating around 300 or possibly a little less. There is some of math involved, but if he really wants to change his armour absorption, it can be done rather easily.
But if you can't be bothered, just stay ontop of your displayed AR and try not to go over 300. DON'T improve your armour too much, don't enchant with damage absorption and for crying out loud don't use dragon armour!!!
And yes you can increase your armour rating without even using a single piece. To get 80% absorption you would need around 667 displayed armour rating without any armour peices.
It is NOT GIMPING your player if you choose to lower your AR by neglecting certain skills and NOT wearing top tier enchanted armour. It's a game mechanic in use forever in TES series.