Uh i would say f/p is third since we're stuck at petris til 200 and i/l and bishops can o2/o4. 1. I/L or bishop 2. I/L or bishop 3. F/P 4. Everyone else
Just look at the rankings and count how many of each class are lv 200, that should give you a rough idea.
1)beginner 2)f/p arch mage 3)shadowers 4)bishops as a beginner, there's only two attacks, which is your basic attack and your snail shell. it requires nearly no skill or mechanics to get the job done. nothing special, no fancy combos, nothing like that. just press 1 button repetitively. boring? yes. easy? definitely.
As opposed to other classes? Come on, pretty much everything has like two or three offensive skills they use until 4th job. At least it's more challenging to avoid damage and aim your melee hits as a beginner