So a quick search says that "A Hero is Need" is the 4th to last quest of the 2.0 story. The most recent update trimmed some of the upcoming quests, so that would put you roughly 84 quests from entering the city of Ishgard and unlocking Dark Knight(and astrologian and machinist if you decide). That sounds like a lot. We can break it down. You have two dungeons, two full party dungeons, 3 alliance dungeons, 9 trials, and a handful of small solo fights - plus the story beats wrapping up the current tale and working its way toward the gates of Ishgard. So how long does all that take? Depending on que times(as a tank, these should be short) and how fast you read thats 6-12 hours roughly. But if you are feeling kinda burned out, i wouldnt recommend doing a hard push.

What i would advise is to finish the 4 quests of ARR. You have a date with an Ultima Weapon, Gaius, and Lahabrea - best not keep them waiting too long. For some people, that climax of the ARR story serves to re-energize them. If this is you, then push at least a ways into the 2.x quests(the more you do, the less you have left to do). If reaching this conclusion doesnt help with the burn out, then put the story on the back burner for a little bit. Beating 2.0 means that a bunch of optional content becomes available to you to do all at once. Someone whos engaged is advised to skip a lot of this and come back later, someone who needs a change might enjoy some optional dungeons/trials/side quests. Doing some Hildy(comedy side quest series), trying out being a post moogle(world building/comedy sidequest series), maybe doing some fates for a Yokai weapon/mount(limited event currently running), testing out PvP, starting a relic weapon(excellent glamour), or even just bumming around the casino and playing cards/racing birds.

If you do the "slow down" route, i also advise immediately taking the quests for the parts of the story that you can do whenever but need to finish before you can move on. This is the re-fights with Ifrit Garuda and Titan(same basic fights, but scaled up to 8 man since all trials moving forward are 8 man - the quests start in the waking sands) and the Crystal Tower series(starts with the "Legacy of Allag" in mor dhona, leads to the 3 alliance dungeons). All of those need to be completed before you can finish the 2.5 quests, but you can do them as early as you want so put them on your radar right away. Beyond that, doing a few quests whenever you log on doesnt hurt. It seems like a long list, but every little bit you whittle away is a bit in your rearview mirror. How many quests did you to do get to this point? Easily twice as many and without a clear goal in sight. You can do this!