The am fah, as you've noticed use traps and they're really annoying. Trapper on trapper is kinda funny, try it in the zaishen elite as a trapper. In general these guys do not pose a threat on any level so feel free to experiment with anything.
With afflicted my reccomendations are a little different... heehee
get a looooong range bow and use barrage with splinter

you do NOT wanna be trapping when things get dead (think assassin tank wannabee but with vastly superior armor

).
It's kinda too bad though, in factions there are many many giant mobs of densely packed critter that are perfect for barrage. I really like running in Gwen where things spread out more and other builds are actually vastly superior. That said, anywhere barrage is good so are traps, but they're more dangerous to place (unless you prep with them and then aggro). I do like to use a pattern of drop a single round of traps then aggro. Once things settle a second run up behind the tank and drop them as they fight. Escape is also quite good in a dedicated trapper bar with dust, barbed, tripwire(great for knockdown combo with barbed) and perhaps flame trap as it will last long enough to get several traps down and get away again. Choking gas is fun in factions as well due to aoe, just use it up, then while its down drop a few traps.
Overall though, a trap or two IS good even if you are running a mass splatter damage build such as for afflicted. Other skills may be good as well however, but I do like to drop a barbed trap or such just as a defense for the backliners in case aggro breaks and some come after the monks. At least the monks will be able to kite easily from crippled melees. The only problem you face here though is the attribute point spreads, so consider a WS based build like apply cripshot and a trap or two.