2: There have been many a suggestion regarding potential ways to make traps a little more balanced, and here's my two cents: If a creature is aware of a trap in that square, they can move through it at full speed with a small chance of accidentally setting it off, or they can (and this would be the default behavior for dwarves) move while "prone" and be safe. This makes main corridors full of razor-sharp traps far less efficient. Thus, it would be wise to have a few separate entrances, or some other clever way of mitigating the slowdowns. Note that adventurers might later on be able to spot traps and choose for themselves whether to dash through the spinning blades, or just try to crawl through safely.
I tend to rank cage traps along entrances (if a force is trying to rush through, then the lead invader triggers one and the next in line triggers the next, etc), if I use them, but one could apply the same methodology to weapon traps that might jam (and of course anything where a degree of reloading is required). Obviously cage traps are strictly one-use only (without intervention), so a creature becoming aware of its existence from its activation by another of its ilk really doesn't occur (unless you sneak reloaders to the trap from a side-door when the invaders have passed deeper into your convoluted entranceway), but I suspect that it's the "I saw my comrade killed by a big spiked ball" concept that you're talking about.
Perhaps the caution could be applied to neighbouring/nearby traps, though. Ooops, lead goblin got trapped in a cage. Second-in-line goblin is then cautious for an arbitrary number of further steps through the corridor while avoiding (or trying to spot, so he can avoid/point out to his compatriots) the next trap in. Though at some point he'll have walked far enough without sign of traps (maybe over them, but in an ultra-cautious mode not matched by his ability to observe the fate he narrowly missed) to start running at full speed again.
Now, this has plusses and minuses for all. Overtrapping could increase the cautiousness and trap-finding proficiency of the invading force to a degree where few further traps can claim the remaining bods (as long as they aren't sitting huddled in a corner of your complex, by this point, too scared to move). On the other hand, the occasional trap could be a useful speed-limiter to a force, making them move at half or quarter speed along perfectly safe corridors and let you muster your forces.
It could be linked to trap-types, and perhaps a bit of positional randomness. Having encountered several giant axes swinging from the ceiling, which are now being looked out for through the tell-tale ceiling openings, there's still a surprise element when the spikes pop up out of the floor through the previously unseen gaps between the cobbles and the serrated disks come out and slice down the walls along head-height slits. And anyone who survives that suddenly discovers he has been engulfed by the cage that was laid out flat in the grassy inner exit to the settlement's compound...
Obviously it would need to be extended to enemy-activated pressue plates, though manually activated anti-invader responses would be a different matter (except, maybe, so far as to designate certain tiles as ones they should try to avoid, and maybe recognise later atom-smasher layouts, "dunking bridges" and "hot hatches" in order than safer paths might be attempted, either in continuing the near-suicidal charge inwards or in the process of escaping the Pramid of DOOOOMMMM! that has finally broken the spirit of the survivors.
Or something.