In particular, in the earlier parts of the series, Theck discerned the new formula for working out each avoidance stat after diminishing returns. As a result, he was able to plot out (for plate tanks in particular) the proper ratio that dodge and parry should be balanced at.
Right now, on live, we want to keep parry and dodge as absolutely close as possible. The two have the same diminishing returns curve, which means that x points of parry will be diminished exactly the same as x points of dodge. As such, if you have 3% more parry than dodge, you're losing a non-zero amount of avoidance to the gaping maw of diminishing returns that you might otherwise keep if it was reforged to dodge.
However, as Theck has discovered, the DR curves were bent significantly apart in Mists, to the point that we'll want much more parry to keep an even ratio with dodge -- about three times more parry, to be exact.
To use the author's own words to describe how crazy the curve is:
This plot tells us exactly how bad the discrepancy between dodge and parry is. If we have 10% total dodge on our character sheet, we'd want to stack up to 21% parry to make sure that we're not being inefficient with our diminishing returns. And it gets worse as we go higher – at 15% total dodge, we'd want 39% parry, and at 20% dodge we'd want 57% parry. The ideal ratio of parry:dodge gets larger as we stack more dodge (though to be fair, this is only because of base dodge and parry – the ideal ratio of pre-DR parry and dodge is a constant).As it stands now, plate tanks are going to need a calculator every time they get a new piece of gear, if they don't want to accidentally toss any free avoidance out the window. Another option: Keep a browser tab open at Ask Mr. Robot.