There are actually several Defensive Stance sets with the same name and effects. Items from a different set will not contribute towards the set bonus in another set. In other words, you will not get a two set bonus for just wearing both a Druidic Bracelet and a Stone Tower Earring, since they belong in different sets.
EQ2i credits this article at Census for the info in this article. the last update on Census for this item was: Tue, 18 Sep 2018 15:00:08 +0000