Prefer a defensive build when tackling new content, and I'll switch to STR as we become more comfortable with the fight, and/or to help with DPS requirements as we become aware of them. My gearing up followed the same pattern, DEF>DPS, but any time I outgear content (more or less all the time) I use STR accessories, and will ShieldOath or SwordOath depending on the healers.

Currently I'm OT for FCoB though because I have an assortment of accessories and MT is still gearing, she's focused on a DEF build for now and I wear mostly DPS accessories.