Don't get too hung up on cp per kill, but also think about the effort taken to kill the mobs. I tend to solo on twitherym in Outer? Ra'Kaznar and get between 1500-5000, depending on rings and chains. Think I just broke the 250 mark on thf, so have some bonuses from that. Haven't finished SoA or the final Rhapsodies, but got the passive bonuses for finishing the other missions.

Basically, I may not earn a ton per kill compared to other options, but I can kill mobs fast with little to no danger to myself. And since 99.9% of my playtime in the past year or so is solo, I'm not hurting anybody else by not being a "job master" yet. Play for maybe an hour or two a day, end up with 3-4 JP just knocking out daily RoE goals.