There's roughly about 200 dps between all the tanks, and if you look at the statistics, PLD is now marginally outperforming DRK on most of the fights following the 6.21 buffs. This is in comparison to DPS jobs that are each individually doing more than 150% of your raid contribution and vary by nearly 1000 dps in some cases.

You should try your best. But the unfortunate truth is that SE has gone to great lengths over the past few expansions to de-emphasize the value of good tanks, and you will not make or break any of these checks outside of grossly underperforming.