Looking at the "Top" DPS parses can also be slightly off, due to people stacking certain jobs to maximize their own fflog.
But what was most important in that fflog was the number of GCDs. 31 more GCDs than you is essentially 76 seconds (1min and 16 seconds) of time, where you werent attacking the boss.
Looking at DA isnt as helpful, since you might not be able to afford to use DA as often, if your party set up isnt designed to make DRK on par with the other tanks. (Such as having a NIN and a WAR, to help maximize your threat. Or DPS who can cut their threat in half, instead of just diversion)
Heck, just having party members who are terrible at DPS can actually raise your own DPS, due to not needing to use enmity combos. (This is why it gets tricky to measure urself to the top spots. And the further u get into savage, the more likely you'll only see crazier numbers, as you'll have less "average" numbers being posted)
But looking at the DAs missed, 24, is 140 potency missed per DA. (Im not sure what the best way to estimate how many GCDs this is equivalent of, so I'll make a poor guess) So lets say its roughly worth 1 GCD (going with an idea that every 3 GCDs averages out the 3 in total as 150 potency) if so, thats 24 missed GCDs, or 60seconds worth of GCDs. So, only compared to the other DRK, you're roughly not attacking the boss for 2mins of the fight. (This one is less accurate, as not using DA isnt the same as not attacking the boss)
Of course, DRK needs a lot of set up, just to get numbers nearly equal to other tanks, and needs to spend all of its MP on keeping its DPS equal to them.
but it would be better to find a fflog that didnt have a NIN in the DRKs group, with a DRK who had nearly equal amount of time MTing, or even more, to then get a better idea of how far behind your DAs really are.
(unless you have a raid group who does have a NIN, and or a WAR.)
Also, you're using STR potions to help raise your DPS right? using them at the right time, like in TA windows makes a good difference in DPS.
EDIT: forgot to add in priority of DA. I havent played DRK since I hit 70, and hated it, but if I remember correctly, your MP should be prioritized for DA+CnS#1, then Blood Spiller#2 next, then on syphon strike/soul eater. (Of course you heal more if you slap it on soul eater, but this isnt a dps increase) dont forget to prioritize delirium to extend blood weapon, over blood spiller. And dont forget to use up your MP, before you hit delirium.
You may be having clipping issues, due to DRKs longer animations/locks, and poor ping. I know I cant double weave on most jobs w/o clipping 80% of the time. 20% of the time, it will not clip.
In HW clipping wasnt as big of a deal, since DRKs oGCDs were higher priority than their GCDs, but id wager not as much anymore, since they lost so much oGCD potency.
Also, make sure the boss isnt going to jump away when you go to use blood weapon/delirium/DA.
If the boss makes u turn away, depending on your ping, try to find out where is the absolute last GCD u can land, before you have to turn away. its a bit hard, when its not consistent, and you have to get a rough idea what is average.
And some tanks will use range attacks in certain mechanics to keep DPS on the boss, but this may or may not be worth the DPS, if you could be using the MP on DA/other stuff, so its hard for me to tell u the answer here.
(On PLD and WAR lob/hawk are easily a DPS increase when out of range)