you see its not like Skills give you more exp, each monster have certain amount of exp that will give to you once killed.
What its happening and “you think” its the reason you get more exp, its not the skill, its the amount of monsters you kill, its not the same to kill 1 monster with dunno magic missile and get .1% than kill a group of 5 from the same monster with earthquake killing all of them will net you of course more exp because you kill all of them at once.
thats why you feel you dont get enough xp with your skill because you cant kill many monsters at once, other classes with AoE Attacks can level faster because that, when i was leveling my Reiter (248) on blue tinis, each tiny give me around 0.3% Exp took a bit because i can only take down 1 tiny at once since Limacon Spread its only a Reiter C3 Attribute, but the speed rate killing them was enough to keep killing tinies non stop since they spawn in other area as soon i clean them in other. While on my Hoplite C3 was easy to get from the same tinies 0.9% or even 1.2% per kill because i can gather them with swash buckling then spear throw killing 3-4 tinies since spear throw its an AoE skill that sometimes Tinies dont spawn quickly enough as they did with my Reiter
Unless IMC have changed something or tweaked the game code, you should try to compared it with another class that its DPS or have AoE skills to confirm what you said.