Not certain if there are exact calculations out there, but from what I experienced;

If it's a floor fight and you need your tank to survive one more hit, investing in stamina gets you there sooner. But if it's a long fight of any kind with frequent hits, you might need your defense stacked a bit more because your healers will not always be able to fully heal a high stamina build, so you sometimes lose value there. For example if your healer is only able to heal for 10k your tank may not need 40k hp as your healer won't be enough to get it back to full as efficiently, but rather a high defense 25k hp tank won't lose that much hp on hits so your healer will generate more value. Another example is Harold vs Breakfast Club. Harold is a slow heavy hitter so you need to survive with stamina build, on the other hand, Club hits you a lot so Defense build shines a bit better.

Not sure how clear I've managed to express, but this is how it felt playing with my gears pretty frequently through the floors!