Just some thoughts on damage for you:

1) Not using a correct combo/rotation will result in lower damage. Certain skills on jobs that are melee orientated chain, and will only do boosted values when proceeded by a certain skill in the chain. If youre just spamming riot blade, it does 100 potency out of combo. Make sure youre using your combos on melee jobs correctly. As others have pointed out, potency doesnt equal damage. You can think of it as a modifier. so 100 potency is 1:1, 200 potency is 2:1, etc etc. So a higher potency means a skill will hit stronger relative to other potency skills. Keep in mind, however that the potency isnt universal to all classes. What I mean is you could have a 1000 potency skill on WHM do less damage compared to a 700 potency skill on another class. The potency concept is only in relation to skills on the class you currently are on, not in comparison to other classes.

Lastly, become familiar with your job. In extremely simple terms, there are two kinds of damage dealer types: Burst and Sustained. Burst types have phases of really high burst damage with phases of moderate damage. This would be something like a warrior who pops their Inner Release and spams Fell Cleave five times for massive damage before returning to normal rotation. Sustained is that your average damage output over time is overall higher compared to burst but you dont have big damaging attacks typically. PLD is more in line with this. You have a few stronger attacks but overall you arent all that bursty. You just do more consistent damage. So if youre seeing a Warrior go up and 2-3 shot something, its cause theyre bursting it down usually, where as it might take you longer to kill it cause you dont have that kind of burst. But on a prolonged fight, youll edge out a Warrior in damage overall (assuming both of you are similar ability and gear) simply because you have better sustained damage.

There are obvious caveats to this, and this is a super simplistic way to think about stuff, but the point is be very considerate to the class your playing. It's not going to necessarily be like other classes in terms of how damage is put out. It may take you longer to kill a standard trash mob cause you dont have that burst compared to a warrior, but you may do more damage to a boss overall on a long fight.

2) Gear. Gear is a huge deal in FFXIV and a matter of 20 ilvls can mean a huge difference in output. Furthermore, there is a stat prioritization you need to consider when dealing damage. In the case of most classes, the first consideration is Weapon Damage, then Primary Stat, then Secondary Substat. 2 Atk no a Sword for PLD is going to matter a lot more than 20 STR, and 20 STR is going to matter a lot more than 40 crit. So to maximize your damage output, make sure your weapon is up to date, followed by your armor and accessories having as much of your primary stat as possible. Try to avoid gear with stats you dont need.

Keep in mind that iLvLs jump up a bit at the level caps per xpac. So at the end of ARR, the default gear is between ilvls 50 to 90, but goes as high as ilvl 130. HW gear goes from 130-270, SB is 270-400, and ShB is currently 400- 505 (and will go up with the next major patch.) 30 or so iLvLs will make a big impact on your damage as well as survivability as a PLD. The typical rule of thumb is if its for your class and its 10 ilvls better than what you have right now, use it. At end game content you can start tinkering with equipment sets to min/max output, but for leveling purposes it's generally highest ilvl goes.

3) Content. Being synced to content will sync gear and stats down to the appropriate ilvl. You still should do relatively more damage with better gear but it wont be your 'natural' output.

4) Party Buffs: Depending your party composition, you will get stat buffs. Furthermore, some classes help improve your damage output with their skills. Certain items will also boost your damage for a small period of time (potions and food).