tl;dr
D8 FIGHT STRATEGIES THAT ARE SORTA TRAPS
1 - single big melee threat/multiple melee enemies engage on ground while ranged attacks from above
1 - single big melee threat/multiple melee enemies engage on ground while ranged attacks from above
2 - single undefended ranged, but after engaging two hidden melee attackers charge in
3 - narrow entry; two slow enemies part and flank
4 - ranged on ledge; back route covered by another ranged
5 - noisy stairs/alarm alert hidden enemy behind
6 - multiple slow enemies in middle of area hazard
7 - single strong slow ambusher, route to easy counter-ambush
8 - extremely strong but almost stationary enemy guarding door
I grew up on 3rd Edition and its strategy fetish and love of granularity, and it never quite worked for me running games. Traps in 3rd are a curious thing. They have Encounter Levels because it occurred to someone that they should give XP and things that give XP need to have Levels in order to be Balanced. They are disabled with a short series of flat Skill rolls. Most deal some normalized amount of damage that is related to their EL and concept, such as an arrow shooting out of the wall, or a more accurate, poisoned arrow shooting out of the wall.
None of these things are necessarily bad, but the way a younger me read them lead to the impression that they were all what Arnold K called “the bad kind” of traps. In Skinnerian conditioning this could be called a positive punishment reinforcer, but without any focused behaviour to be conditioned in an exploration-based game it ends up producing paranoid style behaviour from players, or a fatalistic “life is pain” philosophy.
So back to Dark Souls. A trap encounter can just as easily be a monster placement. These are a few setups from the early game; one just needs three enemy types: normal melee attacker, slow but heavily armed and armored, and ranged.