
Wall of text incoming.
There's been quite a few people with concerns about how sketchy the skill-up system is, so don't get the feeling that it might just be you having issues.
Personally, I feel the skill point system to just be an all around bad idea. I even sent in a feedback to SE (And believe all those who feel the same about the skill point system should do the same.). Basically, you get skill points through various sources. Using an offensive ability that does damage to an enemy, parrying an attack, blocking with your shield (For sentinel skill points), and healing party members while engaged in combat in a party. Basically, every swing has a chance (Presumably based off RNG) to grant you skill points. The higher percentage of damage to the enemies HP, the more skill points are awarded. The downside to this is that using higher hitting attacks kills enemies faster, and if you aren't granted skill points off the larger attacks you gain less overall.
So, you can either kill mobs quickly and have a chance at large amounts of skill points, or kill them slowly with "Auto" attacks (I.E Light slash, stab, etc) and have a greater chance at earning skill points overall, albeit at a smaller amount.
However, it's highly possible (And happens often to me) to receive barely any skill points from enemies no matter what you do. I can fight a green or yellow marked enemy at level 20 and walk away with 30-100 skill points (Which is what I usually get), and it takes me about 1-3 minutes to kill them. Sometimes I walk away with 300+ on a yellow enemy, but that's a rare occasion. Overall, I usually get about 2000-3000 skill points an hour with diligent grinding, which is just silly considering I need 20,000+ these days to gain one level. It shouldn't be taking me seven hours for one level at twenty, you know? I can't even imagine what higher levels would be like at that rate. Forty eight hours of gameplay to go from 43-44? No thanks. It also doesn't help that most enemies are very scarce, and there's usually at least one other person around leveling in your area, no matter how far out you get. Most of the camps have been staked out by this point in the game within the 1-25 level range.
Partying is also sketchy with this system. Let's take Gladiator for example, since I am one and have had first hand experience. A Gladiator has to keep his shield arm up at all times while tanking. We just do, it negates a ton of damage. However, holding it up takes a solid 5-10% of the stamina bar or so. Not to mention the process takes a second or two to register. Now, we also need to more or less spam provoke at this point in time to be able to effectively hold aggro over the other classes. Provoke takes about 25% of the stamina bar. Mixing these two stamina-draining actions together leaves the Gladiator without much time to get in melee swings by the time the enemy is dead, and we gain barely any skill points compared to our party members. Healers are in the same boat, as they don't receive much from healing.
All of that aside, it's important to take into consideration the fact that the game is still learning to walk, and hopefully the majority of this will change regardless of whether or not SE receives feedback. I honestly believe they just need to do away with skill points on attacks and heals, and allow us to receive a set amount of skill points upon kill, just like we should. I hated FFXI's skill up system for weapons, and all they did was turn that into the way to level your class itself. Just not a great idea in my books.
There's been quite a few people with concerns about how sketchy the skill-up system is, so don't get the feeling that it might just be you having issues.
Personally, I feel the skill point system to just be an all around bad idea. I even sent in a feedback to SE (And believe all those who feel the same about the skill point system should do the same.). Basically, you get skill points through various sources. Using an offensive ability that does damage to an enemy, parrying an attack, blocking with your shield (For sentinel skill points), and healing party members while engaged in combat in a party. Basically, every swing has a chance (Presumably based off RNG) to grant you skill points. The higher percentage of damage to the enemies HP, the more skill points are awarded. The downside to this is that using higher hitting attacks kills enemies faster, and if you aren't granted skill points off the larger attacks you gain less overall.
So, you can either kill mobs quickly and have a chance at large amounts of skill points, or kill them slowly with "Auto" attacks (I.E Light slash, stab, etc) and have a greater chance at earning skill points overall, albeit at a smaller amount.
However, it's highly possible (And happens often to me) to receive barely any skill points from enemies no matter what you do. I can fight a green or yellow marked enemy at level 20 and walk away with 30-100 skill points (Which is what I usually get), and it takes me about 1-3 minutes to kill them. Sometimes I walk away with 300+ on a yellow enemy, but that's a rare occasion. Overall, I usually get about 2000-3000 skill points an hour with diligent grinding, which is just silly considering I need 20,000+ these days to gain one level. It shouldn't be taking me seven hours for one level at twenty, you know? I can't even imagine what higher levels would be like at that rate. Forty eight hours of gameplay to go from 43-44? No thanks. It also doesn't help that most enemies are very scarce, and there's usually at least one other person around leveling in your area, no matter how far out you get. Most of the camps have been staked out by this point in the game within the 1-25 level range.
Partying is also sketchy with this system. Let's take Gladiator for example, since I am one and have had first hand experience. A Gladiator has to keep his shield arm up at all times while tanking. We just do, it negates a ton of damage. However, holding it up takes a solid 5-10% of the stamina bar or so. Not to mention the process takes a second or two to register. Now, we also need to more or less spam provoke at this point in time to be able to effectively hold aggro over the other classes. Provoke takes about 25% of the stamina bar. Mixing these two stamina-draining actions together leaves the Gladiator without much time to get in melee swings by the time the enemy is dead, and we gain barely any skill points compared to our party members. Healers are in the same boat, as they don't receive much from healing.
All of that aside, it's important to take into consideration the fact that the game is still learning to walk, and hopefully the majority of this will change regardless of whether or not SE receives feedback. I honestly believe they just need to do away with skill points on attacks and heals, and allow us to receive a set amount of skill points upon kill, just like we should. I hated FFXI's skill up system for weapons, and all they did was turn that into the way to level your class itself. Just not a great idea in my books.