During campaign I regularly get 300+ JP/hour at Reisenjima #2. Two BLUs cleaving, one on each side, people in the middle. That said I feel the CP is better on apex mobs, but you don't get any silt/beads/vorseal credit for apex mobs.
if you do 5 south in the place with chigeos, frogs, lady bugs, mantids, you can get 8400kcp/hr with one blu self aoeing and someone else keeping chain, we hit 9800k/hr when we invited a few more weaker melees to help keep chain. Ended up getting 500 jp in a little over 2-2.5hrs and chain 1000+ before we had to spend points. I was on rdm 2 shotting mobs with spells and a friend was on blu pulling and self aoeing, various melees (thf, nin, weak blm leech) joined which i stopped to haste and occasionally cure while chaining. It was def great for silt.