Dual-wielding set items

[Thrugg]

do you get any extra bonuses for dual-wielding two swords and two rings of the same set?

There are two kinds of set bonuses, the ones that are displayed on all the items in the set in gold, and the ones special to each item that appear on that item in green.

Wearing multiple rings or swords will not increase the gold bonus at all, whether you are wearing a full or partial set.

However, the duplicate set items will both get their respective green bonuses. In the case of wearing two rings, you will certainly get double benefit. In the case of swords though, you will only double any passive benefit on the swords (eg +Str or +life). +AR or +damage that only applies when you hit with a weapon, will naturally only apply when that weapon is used. You only hit with one weapon at a time, so typically you only ever get that benefit applied once. This is the case for any dual-weapon setup though, not just your set scenario.