So this might be kind of a dumb question, but why do monk abilities in general have lower potency than most other melee classes? Like, what is their damage supplemented with to make up for that difference? Considering the self-buffs the other melee jobs have access to, I can't imagine Greased Lightning evens things out by itself.
Like, especially given the positional requirements, just by going by potency numbers it looks like monk would by far be the worst melee DPS class to solo quest with (as stuff will generally be facing you)
For DPS purposes, Greased Lightning is, when fully-stacked, a 50% DPS increase. Greased Lightning is 10% damage and 5% weaponskill and autoattack speed per stack, and you can have two stacks at level 20, and three at level 40.
Twin Snakes gets you a 10% damage buff. Dragon Kick makes enemies take 10% more blunt damage (which comprises all of your damage). Fists of Fire will passively grant you 5% damage when in that stance.
These are buffs that, unless the boss goes away or you're otherwise forced to not be attacking something for an uncomfortable amount of time, are pretty much always active. That's 45% increased damage, the target takes 10% more damage from you, and you're doing all of it 15% faster. Consider that MNKs are balanced around the fact that in boss battles, they will periodically be forced to drop stacks of Greased Lightning.
This means you're going to be pretty much passively running at 183.425% of the DPS you're at before being stacked.
On top of this, they also get a very, very potent cooldown in the form of Internal Release: 30% increased critical hit chance for 15 seconds, on a one minute cooldown. This critical hit chance bonus is
additive - so if you normally had a 20% chance to crit, Internal Release makes your total crit chance go to 50%.
On the surface, sure, the numbers make MNK look like it should be doing comparatively little damage. In practice, and after understanding how all of these work, MNK ends up being one of the highest-DPS jobs in the game (they were previously the highest, but that mantle belongs to SAM now, who is pretty much completely devoid of utility).
As for soloing, keep in mind that Fists of Earth grants you the best persistent defense of any non-tank job (it puts you in a better defensive position than even DRG's heavier armor class), and that you can also stun enemies the most often out of any job in the game (as one of your second combo step abilities, One Ilm Punch, can stun enemies in a way that isn't subject to stun resistance buildup - on top of having access to two oGCD stuns in Shoulder Tackle and Leg Sweep if you take that as a role skill). So while going purely-solo, you may not match up in damage, you'll be at a defensive advantage compared to most jobs, save for those in tank armor or able to heal themselves or have mass crowd control.