Warden-UK wrote:Is there a situation wherein individuals wearing certain armours cannot be hurt by certain types of weapons, ever?
Absolutely. But that is far more of a matter of Defense and the Ability rating used to attack than it is of Armor Rating and weapon damage.
If you cannot get enough degrees of success to multiply the base damage of your weapon to a high enough total to overcome an opponent's armor, you are incapable of hurting him, yes. There is a reason there are figures in Westeros that no one in their right mind would think of attacking one-on-one.
Warden-UK wrote:And is it the case that platemail loses its effectiveness the higher it goes?
Sorry, I'm not sure what you're asking. "the higher it goes"...what is the "it" you're referring to here?
The rules in Song of Ice and Fire Roleplaying do a pretty fair job of reflecting situations in which superior opponents, with superior weaponry are nigh-unkillable against lesser individual opponents. Jaime Lannister, the Mountain, the Red Viper of Dorne, Barristan Selmy and similar men of renown for their fighting prowess are rightly feared.
That said, they also reflect fairly well the situations in which these men might be still overcome: where mobs or armies are concerned. The Assist rules reflect the kind of increased chance of getting hurt even the best of these warriors stand. Even average fighters with no real training (Fighting 2) offer a +1 to Fighting tests if they're helping someone else. This can make the difference between such individuals being untouchable, and them taking a bit of damage every turn.
Additionally, there are other Combat Actions that benefit a weaker opponent. Grappling an enemy with the Pin
action is extremely useful, especially when fighting in a group. If one or two of the group Pin an enemy, everyone else gains a +1D to their Fighting tests and the opponent must subtract his Agility from his Combat Defense. So, some of the group dogpile him, and everyone else gets in some stabs with a suddenly much better chance of hurting him.
Other actions like Knockdown
(see Advanced Combat actions) can be extremely useful, as well, particularly since it is an Athletics test against your opponent's passive Agility - and short of water dancers, most fighting types don't have a very high Agility, making them susceptible to this move. Once down, opponents gain a +1D on attack rolls against the downed opponent.
If the opponent's Combat Defense is just too high to hit, the Distract
action is of great facility, forcing him to subtract his Awareness from his Combat Defense with a Cunning test against the opponent's passive Will.
The key to success, of course, is stacking these actions. A group of opponents can confuse, knockdown and then dogpile a single opponent in short order. Perform a Distract to reduce his Combat Defense, followed by a Knockdown to grant everyone a +1D on attacks. Others perform a Pin, granting another +1D (for a total of +2D - that's not nothing) and reducing his total Combat Defense to only his Athletics (as Distract subtracts his Awareness from his Defense, and Pin subtracts his Agility).
At this point, any others left in the group start going to work with their weapons on the fallen, pinned, confused enemy. Each one is making a Fighting test at +2D against a Combat Defense that equals only the fallen opponent's Athletics - you're sure to get more than a few solid hits in there.
This is the mob scene in multiple points of the Song of Ice and Fire
storyline, where the knight is buried under attackers, prevented from moving and stabbed until he stops moving.