Trap Placement Question:

[Inutile]

Does the offhand weapon affect trap placement speeds? Does IAS on the offhand matter?

[aoaa]

Does the offhand weapon affect trap placement speeds? Does IAS on the offhand matter?

IAS for your trap laying speed comes from all items EXCEPT off hand claw. It's also determined by your base claw speed.
Greater Talons and Runic talons(Claws most used) have a base of -30wsm, so if you're using 2 of those you only need 42ias for 9fpa trap laying, the fastest it gets.

[Inutile]

So it averages the two claw speeds when dual wielding?

[aoaa]

So it averages the two claw speeds when dual wielding?

Yep.
Say you have a -20Wsm Claw(Feral Claws) and a -30Wsm claw(Runic Talons), you'd have -25Awsm so you'd need whatever that requires to hit 9fpa.