Actually, you're wrong. JA proccing is better than magic and WS proccing because you can do it faster.

You can expect to take about 2 minutes per monster proc spamming Dia.
You can expect to take about 2 minutes per monster proc spamming WSs
You can expect to take about 30~45 seconds per monster proc spamming /DNC JAs.

That's the disparity that should be fixed. SE seems to have designed magic and WS proc rates with AoE proccing in mind, but they never adjusted them when they nerfed AoE proccing. I used to Aeolian Edge proc city monster pulls instead of JA proccing because it net me about the same currency and let me use camps that JA proccers avoid. I could see SE believing a BLM/RDM spamming -aga III/Sleepga or would do the same thing.

In CoP zones AoE proccing is nerfed and they haven't buffed the single target proc rate enough to make it feasible. This leaves us with three sets of EP monsters per time window, which is insufficient to deal with demand.