PC Causes of Death:
- Combat: 9
- Use of artifact: 1
- Collecting yellow mold for use as as a weapon: 1
- Dungeon traps that a thief could've hypothetically found and disarmed: 1
- Combat: 17
- Use of artifact: 1
- Betrayed by employer: 1
- Opened a box full of wraiths: 1 (not really a combat, per se, nor something a thief could've disarmed)
The Dungeon Phalanx of two ranks of shield-and-spear fighters in front of wizards addresses combat in general pretty effectively. Area effect traps, and traps whose activation is delayed at random (as is the default for ACKS' traps; see page 240, where traps are mentioned as having a 1 in 3 chance of triggered when a character might stumble on their trigger), counter the dungeon phalanx by punishing high densities of characters and hitting the wizards in the middle instead of the shield wall in the front.
But, mechanical traps are dumb and strain my suspension of disbelief, so I don't use them. Seriously, I can't bring myself to build deadly traps into the very architecture of a space that somebody once intended to live in, except to secure the front door, the vault, or a few other high-security spaces, and even then it requires some serious mechanical ingenuity on the part of the original builders for things to plausibly be still running (ie, dwarves yes, humans probably not, beastmen almost certainly not if the trap is any more complicated than a sharp stick with poop smeared on the end).
With no traps, or weak traps, or very few traps, there's not much incentive to have a trapfinder out in front of the phalanx. If your thieves never go out in front of the shield wall, they're likely confined to the rear of the phalanx, where they get to attempt archery into melee at a stiff penalty, and are forever denied the opportunity to backstab and hide in shadows. Further, without darkvision, thieves are effectively unable to scout for monsters (beyond listening at doors), because by the time the thief has seen a monster, the monster has seen the party.
Ergo, "thieves suck". Even if they were good at what they do (contentious), they can't really do the one thing that my players spend most of their time doing and care most about (killing monsters before they kill you) within the local metagame. They do not solve any of the problems that my players have.
I could use more traps, but I really don't want to. The correct question, I think, which will also benefit assassins, explorers, bards, bladedancers, and others, is "what can I, as DM, do to change the Phalanx metagame so that characters who neither wear plate nor cast spells matter in combat in the dungeoneering levels?" And that is next post.