There seems to be a misunderstanding. WS and JA proc at the same rate, tested time and time again. The issue is you can do 10 JA in the time of 1 WS. So, the rate seems lower. MA on the other hand is lower due to the speed spells can be cast 5 spells for 1 JA if you do it right.
The other issue, and this is touchy is the speed enemies die vs respawn. (What I don't want to happen is mobs gain boosted strength) One player can take out 5 enemies in the time of a single respawn. 6 players can wipe an area clean of a mob type.
I think the biggest issue is in dreamland since over all currency drops fastest there, so its most populated. The main issue is the bottle neck system on JA, even with higher rates on MA and WS, JA will still be superior since /dnc is a useful subjob for melee vs say /rdm or /whm. (not saying /mage is impossible but in most cases its inferior) With mobs cycling JA weakness those mobs will continue to be targeted by players seeking currency. I figure allowing all 3 to proc any given nightmare mob at any given time would go a long way to reducing conjestion, even at the cost of lowering proc rates of all 3. I understand its set the way it is to be a limiting factor however, players just run from mob to mob instead of camping one. (its not very effective)