I've heard you say that the Ranger is the second most abused job, what do you mean?
The White Mage is the most abused job in the game. They have to deal with constant heal, raise, cure, teleport, etc. requests. They have to deal with teammates neglecting them and expecting the world of them. It is a very hard job to be.
Ranger is the second most abused job. They get a lot of requests for parties when they aren't seeking, they get parties fighting over them when they are, and they never get a rest during a party. Why is that, you ask? Well, it has a lot to do with the way battles go during a party.
During your typical party, there is a basic pattern that repeats over and over again:
After the party has found a camp, the designated puller goes out and finds the prey. They then pull the prey back to camp.
At camp, they party kills the prey, reaping the rewards (typically just experience, but often times quest items as well).
The puller then goes out hunting for prey. During this time, the others in the party rest (generally, mages heal, melees wait to be healed to conserve TP).
Once the party is rested, the puller brings the next enemy back to camp for the party to kill.
Rinse, and repeat.
Understand that the Ranger is the natural puller. They have wide scan so they can target and find specific enemies. They have high evasion so they can avoid enemies that the party doesn't want. They have ranged attack so they can pull enemies from a very far distance.
Because the Ranger is the natural puller, they will be the puller in a group that knows what they are doing. What this means is that the Ranger is always on the go. During the down time that the rest of the party gets to enjoy, the Ranger must be out scouting for the next enemy. The Ranger does not get bathroom breaks, the Ranger does not get to go get a drink, the Ranger does not get to rest. In fact, if the Ranger is taking too long to find the next enemy, most groups will generally assume the Range does not know what he or she is doing and will debate booting them.
This is why the Ranger is the second most abused job in the game. When you are a Ranger, you will always be on the go.
Now, granted, the Ranger can also be an exceptionally fun job. Most Rangers continue being Rangers because of how much fun they can be (and how helpful they are when farming NMs ;-) But playing as a Ranger can be exhausting.
Is the Ranger the biggest damage dealer in the game?
I hate questions like this. The simple fact of the matter is that all jobs have their place in well balanced parties (except for maybe Beastmaster, although a party of Beastmasters with different subjobs can be pretty rocking!)
Now, IF a Ranger is well equipped with the best weapons, armor (that boosts AGI, DEX, Accuracy, etc), and arrows, and IF their attacks hit, then yes, they can outdamage pretty much everyone else in the game.
However, those are pretty big ifs. The simple fact of the matter is that being a Ranger is expensive, and it can be very hard to get all the best equipment for your Ranger. Hell, just keeping yourself stocked up on ammunition can be a small fortune in itself. Then there's the whole accuracy thing. Many times your arrows will miss (even with Sharpshot, which, until you hit 14 and can wear the necklace, is next to useless) and you will easily be outdamaged by those with more consistent attacks (such as Monks).
You say the Ranger is the natural puller, does this mean they should always be puller?
No, they shouldn't. Obviously there are going to be some areas where someone with provoke or a mage with magic will do a better job. You should always (and I say this over and over again) evaluate each situation.
Also, you may party with a Ranger who simply can't pull worth crap. Pulling is an art, it's not a skill that you learn in the game. It is difficult, and can be tedious. Anyone can pull, but not everyone knows how to pull.
Generally speaking though, the Ranger is the best class for pulling.