Base DEX + something like 490 Parry (which is the average for a lvl 50 WAR I'd say) would've been a control, here it serves no purpose, the numbers are unrealistic.
Base DEX + 456 and base DEX + 486 would've been perfect here.

And what are you talking about for rings ? If you don't hit the threshold without them and you hit it when you add them, they do give you additional % chance of parrying.

With a fixed 456 parry, going from 216 DEX to 266 gives you an additional 4.72% of parrying.
With a fixed 483 parry, going from 216 DEX to 246 gives you an additional 3.55% of parrying.

From the looks of it, the threshold is around 246, meaning you need the DPS rings to reach it, meaning that those ring unlocks you this additional % of parrying, which looks like to be around 3%.

And again. If you grab tank acc, what are you going to meld that will do a better job that this DEX threshold with the last slot ? I'm curious.