Even if all your assumptions are corrct, you are equating 1% mitigation as being equal to .72% more damage. 1% mitigation randomly applied throughout a fight is largely useless unless you have less than 1% overheal (doesn't happen). Any tiny gains in overall mitigation that occur purely on rng are highly unlikely to have any effect due to heals. It's not predictable preventing healers from using 1 more gcd of damage reliably, nor reliable enough to help on busters which are precast abilities and heals anticipating damage. This is of course in a raid environment because in 4 mans, no gear matters enough to loose sleep over optimization fighting a 3 mob pack in a dungeon.

1% mitigation spread haphazardly through a fight will just get absorbed by over heals and buster anticipation. That's why I take issue with the idea that you can even compare damage reduction with dps in a direct 1 to 1 level as if they are equal. If everyone in the party min maxes for 1 to 2% more raid damage it's a notable gain of 5%+ raid damage combined (say every weeks new piece of tpme gear for the group). But mitigation is is only effected by tank. There are no combined small efforts from they group. Only from tank armor/hp/and parry. 2 of which you will get from any gear regardless of secondary.

In all cases the dps boost us small as is the parry boost. But the parry system has so many systematic reasons why it is weak that it becomes virtually zero effect in any actual situation (shields proc 1st. Abilities tat increase blocks or parry reduce the relative effectiveness like better ilvl shields, buleark, sheltron, raw intuition, dark dance etc, tank swaps forcing everyone to OT making parry useless for half of most fights, the preemetive use of abilities and heal timing for tank busters making a parry on a buster wasted, the nerfing of parry str scaling in 3.x, and on, and on and on. Parry is systematically neutered at every turn.