I was thinking through the issues with tanks wanting to use lower ilvl gear, and I'm starting to wonder if the determination and tenacity stats are **ACTUALLY** currently bugged, and not providing nearly the bonus they should be.

That would actually explain a lot, as IMO Tenacity should essentially be determination with more stuff - which would let tanks to put more emphasis on tenacity, skill speed, and/or crit instead of trying to stack more strength.