Factors you may or may not realize.
(1) a Job has higher stats, and those few points can really make the difference at certain level ranges. (u get 1 more flash worth of MP as WAR compared to MRD)
(2) threat is the biggest issue in Halatali, and if you're a WAR, in Totorak as well. (Once u have a tank stance, u can literally just spam your weakest attack, that has no threat, and still hold hate. I dont even use my threat combo as WAR unless im trying to maximize my DPS)
(3) If your DPS is really good, and they dont miss a beat, they will surpass your enmity per second in those 2 dungeons. (excluding PLD or DRK in totorak)(done a lot of tests on this to prove it)
(4) if your gear isnt syncing down to the dungeon your gear will be weaker than any teammates who are syncing down. (A change made back in 2.x) So if its a Lv20 dungeon and you have an HQ Lv20 weapon, it will be out damaged by a Lv24 weapon synced down for the dungeon. (Which matters a LOT for threat. a single point of weapon dmg is DRASTIC)
(5) your threat combo currently generates less threat every 2 GCDs than your AoE (overpower) does every 2 GCDs. so if you use that instead of your combo, you can get a lead back in enmity. (Also if the DPS is TOO bad, the fight drags on, and u use more AoEs to hold hate over healers, which leaves u with less next fight too. But this happens rarely now, but was common in 2.0 when AoEs generates MUCH lower threat, and PLDs had a 3.5s GCD instead of 2.5s GCD)
(6)use VIT food. Seriously makes a difference in your dmg/threat if you're new to a dungeon and still need to get its gear. (not as much as a new weapon does though)
(7)be the 1st to hit a mob. in Halatali, as PLD, the average enmity per second you can generate with a threat combo, is something like 95-98% of the threat a DPS can generate (depending on gear and such factors) Which means, if you both hit at the same time, you will only get further and further behind. But if you get a full GCD ahead of them, it will take them many many GCDs to catch up to you. in most cases, the boss dies right as they are a few GCDs away from pulling threat. (This can only be tested with 1 DPS not participating in the boss fight)
So make sure to always be the 1st there, but if a DPS gets to a mob, pulls, and gets a full GCD ahead of you, the ONLY way to hope to get threat back is provoke, and hope that they arent perfect in their DPS rotation.
(8) you can not beat a WHM/CNJ in threat if they go full DPS. Cleric stance and stone2 spam is unreasonably strong, and if they are equally geared as u, or worse, CNJ with raging strikes, blood for blood, etc, there's nothing you can do. (They will of course be tanking, and I can hold 100% threat, if i know for a fact i wont die w/o receiving heals on the boss)
So in theory, as long as you play perfectly, you have a very high chance of holding hate 100% of a run. But if you have BLM/WHM who sprint to the next mobs, to make sure they attack before u, there's nothing u can do to keep up with that. (most dont do this anymore, but was pretty much the standard back at release of 2.0. I think ive seen this happen only once or twice since 2.2+, excluding the times ive done it, just to prove to some tanks who claim they can hold perfect hate against me.)