With that out of the way, rolling for armour.
It comes in three tiers for simplicity and parity with Lamentation's own ideas of how weapons work. When struck by an assailant one need only roll the number of d6 associated with the armour worn and reduce incoming damage by that amount, as follows:
Light - Great coats, gambesons - 1d6
Medium - Chain armour, brigandines - 1d8
Heavy, fully articulated, rigid nonsense - 1d10
To compensate for the addition, a subtraction must be made (symmetry must be done). Therefore, armour no longer changes AC. Now AC represents something more akin to good footwork and parrying, rather than taking it on the chin. Rename it to "defence" if it makes you feel better.
Shields work by allowing the wielder to add 1d4 vs. any one blow. This may be chosen at the time of rolling, but before the dice are thrown.
Anyone in defensive stance can add a shield's 1d4 against all strikes in addition to the usual bonus. Parrying also gains this benefit.
Reasons that this is The Best Thing: Other than forming a fearful symmetry, it allows a shade of active participation in blocking and a touch of randomness. Also, high ACs are incredibly boring and create long periods of not much happening. Rolling for armour will allow there to be little victories scattered along the winding road to popping that tin can open.