Well first of all one must understand that yes their is a hiearchy in reference to some skills. For instance EVASION > SHIELD > GUARDING > PARRYING.
Obviously evasion completely avoids all damage so is favored over the others. Shield comes next and is favored over the other for the simple fact that you are putting an object between u and the mob where the object absorbs most of the damage taken but you will still sustain some damage. Sheild obviously is also better skilled up while only holding one weapon and using a shield. Guard and Parry seems more situational with guard seeming to take more effect when a person is utilizing the H2H weaponry and parrying seems more likely to skill up with those who use dual wield more often.
Another factor one must factor in is that the level of our skill is a separate entity from our actually job level. It is possible to be a level 95 Drk and yet only have the Scythe proficiency of a capped level 70 DRK. With that said when skilling it is probably best to skilling based on your skill level and not your actual job level using the Skill chart you see on the wiki. in general you want mobs that are closer to your skill level (-7 to like +3) than your job level because simply put if you cant land the move you wont really skill up that often. Though yes even with that tidbit of information skills are still horrible for defensive skills and some magic skills. Anyway you cut it though the level of your intended target in comparison to your actual skill level is a bigger factor than actual job level.
Just like you wouldnt go trying to kill a level 80 mob at level 40 and expect to be successful how could one expect to skill up at a decent rate against a level 80 mob with a skill at around level 60?