I do apologize for my last post I was in error and didn't notice any connection but i do notice a connection between 1 or 2 key item time extensions increasing proc rate dramatically or as a whole they are:
Amber Granules of time OR Alabaster Granules of time. After we obtained one of these items the proc rate shot up dramatically which may help in proccing. We killed both TE mobs after we attempting to farm.
I do not like taking information from other forums because quite frankly, I don't trust them so I try to post what I find in one area instead of having people flame with no real reasons. So I do apologize and admit I was wrong in some cases, however we have found much information on our own without the help or theories from other people.
Staggers Do seem based on mobs type that remains unchanged and the job abilities are random and do not stop longer recast JA such as weapon bash from proccing, which could cause a problem in the long run, the times we proc on first use and spam is far too sketchy to actually tell if it is indeed random chance to stagger with JAs or if the mob picks a JA to be staggered with at time of claim.
I believe its more of the "picks JA randomly among pt members" and gives a set percent chance of that specific JA working, because we held a mob for 5 mins spamming every single step and flourish we had on it, at the end the DRk walked up and used weapon bash and staggered it on first use. So its still unsure at this time.
Spells meh idk its mainly still the same specific spells listed that are staggering more then anything else, more enfeebles then nukes, still not finding a specific pattern. I doubt SE would make it "Ok this mob will get staggered by spells 2% of the time" I think it is similar to abyssea where the mob picks a spell/ws at time of claim that will stagger it, they just added JA to the list