Don't ever, ever, EVER compare tanks by using sims. EVER.
SimC is not even reliable when using it to compare different talents or gearing strats on 1 tank. TMI, while being the only attempt to measure tank survivability, is still terrible in my opinion. But it 100% has zero credibility when it comes to comparing different tanks.
Defensively, Warriors are fine right now. Probably #1 in Mythic raids.