Admittedly, I don't own and haven't played RtL; maybe that makes everything different. But if so, you should specify that you're assuming RtL. You also should actually present an argument, rather than expressing vague fears and ominous warnings.
You are correct I did not give any examples that should be required.
I play RTL exclusively the last few months so my statements apply to that. I also own all the expansions.
Armor in descent is controlled by avalibility most of the time. This means if you have a hero in chain mail that means one of your other heroes will not have chain mail. This creates the weak link you mentioned and gives the OL a target. This target must then be protectedby the party using placement and guard orders. One of the main reasons the hero that has armor equal to his dice rating is broken is because he frees up a chain mail to be distributed to the other heroes in the group making the group as a whole more difficult to damage.
The party generally moves into rooms and creates a bubble of protection. This is generally done by having the high armor heroes in the front with the lower armored ones in the back. The lower armored heroes then move up to attack and then retreat. This slows the party down as they have to keep close to the weaker members. When an important object is in a room (read dungeon floor in RTL) a single hero can run for it. This hero is usualy either the highest armored hero hoping to survive the counter attack. This of course makes them one of the slower ones so they may not be able to reach the object. Or it is one of the lowest conquest points heroes with the assumption they will die once they get the object (this is important in RTL) I will call this over-extending.
Skills that help this situation:
Grapple, Taunt. Often time these skills force a monster to attack certain heroes or at least not be able to attack the weakest link.
Telekinesis is most useful to over-extending but is mitigated by the fact that the hero attached is often weak.
rapid shot: This skill is most useful if you can get into the center of a room but you risk leaving yourself open to counter attack.
Things I feel two shields unbalances:
Weak back hero. With the addition of the armor ring, the specialty armor, and the two shield build a weak mage hero can increase their armor by 5 for ranged and magic attacks, making them difficult to damage unless you are able to get a melee monster there.
Over extending hero: Now a fast moving hero can over extend with a low conquest value and still have a high armor value for the potential to withstand the counter attack. Adding the fly feat makes this tactic almost impossible to stop.
The average armor value of the party going up is the most difficult issue I feel. This adds the fact that you can now convert one of the usually weak links into a low priority target for the OL and reduce his options of heroes to deal damage to. This will in general increase the number of low damage attacks the OL makes as if the party is moving correctly the weakest heroes should be protect from attack at least some of the time. A party almost always needs a runner. This runner is usually a weak charater with a low conquest vaule. Now this charater can have a low conquest value but not suffer from the weak armor value.
I understand that is is well within the rules to allow. I am just concerned that adding skills, feats, speciaty armor, and the fact that this hero can still attack will remove the weakest link from one hero and move the priority target to a different hero. This new weakest link is tougher than the old weakest link thus increasing the party's entire robustness.
Is this tactic worth the effort? Maybe it isn't.
I dont mean to pick on you granor, and as such I should have clarified my statements regarding dual shields back on the first page.
I dont feel that dual shields are illegal but rather a tactic that has limited application to the underlying goals of descent. Under the proper circumstances dual shields makes a great tactic that could allow a party to withstand fantastic amounts of damage. But the proper equipment, skills, and situation for this tactic to be useful is rare.
I have presided over many descent games, both in RtL and out, and feel that the #1 thing that will kill heroes is a lack of progress. The OL has the ultimate benefit of time with his building threat, drawing cards, and earning conquest, so in order for the heroes to stay competetive (or live) is to keep moving and keep hitting those small goals (get the keys, unlock the doors, kill the boss, escape) to accomplish the bigger ones (aquire conquest and gold, beat rumors, get phat lootz, beat the avatar).
When a hero decides to sacrifice almost all offensive potential by equipping two shields, he becomes reliant on his buddies to make up the offensive difference. And even with the best of skills available to the heroes (knight, leadership come to mind), the number of attacks (and thus the amount of overall offense) that 3 heroes can contribute to a fight will always be sub-par to 4 actively fighting heroes. And when you arent hitting as hard as you can as a party, monster 'waves' take longer to cut through, bosses live a few more rounds, and all the while, more traps monsters and dark events are piling up to slow the heroes down even more. Its called the 'snowball effect', and it leads to some insane lopsided dungeon results (~45 OL conquest vrs ~12 hero conquest, an actual in game result from a single three level dungeon)
Fighting skills Knight, Unmovable, Furr, Able Warrior, and Leadership (and Cleaving, Rapid Shot, Quick Cast to some degree) increase the overall number of attacks (including ones gained from placed Guard orders) that a party can dish out per round, but usually in order to utilize these the best, a party must come to a halt in the dungeon (or at least gain very few MPs) or spend fatigue (which requires slowing down to replenish with rest). By standing around fighting instead of moving forward through the dungeon, they give the OL threat and allow him to dig further through his deck. Most traps are cheap, and even as little as two to three turns is enough to draw/discard enough threat to flip the spawn marker and drop another beastman horde in. And if the heroes are having any trouble whatsoever, they can easily get bogged down and killed. Ive seen games where it is literally a crawl trying to get through rooms, each one taking 1-2 **hours** each. As soon as the heroes felled the last monster of a 'wave', another one was right on top of them again. Through the use of traps and special monster abilities (flying most notably), one can get around the 'wall' of tanks to the squishy guys in the back. Hogging the shields will not help a 8 HP, 0 armor mage that got jumped by a razorwing flying in from 4 miles away. Dual Shielding becomes an 'issue' when the wielder has Taunt (and even more so with Ambidexterious or Grapple). A high armor hero (Nanok comes to mind but hes already been proven to be broken) combined with two shields can taunt any enemy trying to attack other heroes towards it. But this comes at a sacrifice as well; eventually the armor and shields will run out, and (even worse) if the heroes become overwhelmed by monsters the taunter may not be able or willing to take anymore blows. On top of this, a melee attack with no green/yellow dice and no way to spend surges normally is not an attack that will have any real results beyond the copper level (and likely even during the copper level). I recall it being a good idea to encourage heroes to carry two weapons/etc. (This is relevant in regards to the re-equipment of weapons). Not just for countering broken CB cards and Frost, but to handle different situations. For instance, in the very first sessions of Descent, the tanks would frequently carry a sword/shield combo with an axe/dagger in the backpack for those times when more offense was needed. The mage carried Blinding Light for large monsters to give the party a small breather, and Sunburst for groups. And the ranger had the bow for armored beasties and the crossbow for short and heavy damage. Weapon diversification is a key tactic that I feel is vital for heroes to get down. It really makes fighting heroes difficult when they have weapons for horde control, large monsters, anti-melee units, sniping, armored foes....
These are just some things that I and my group have noticed. They have joked in the past about dual wielding two shields, but have never done it; the temptation to deal ~14 damage per blow is apparently just too juicy to pass up.