Hmmm. For my tests I had a tank voke, allowed enmity to decay, then time-cast various spells with a fellow whm, i made sure to keep -enmity constant between the sch and whm (only varying the gown) My first test showed that the mob would always turn to the whm if i had the gown on. If the whm equipped -6 enmity the mob would always turn to me (indicating that the -enm is less than 6.) with -5 the mob would turn to whomever finished casting first.
On my 2nd set of trials I had a rdm instead of a whm and could not replicate the results at all. I even tried actual nukes in the 2nd batch of tests (yes our dmg was the same). Btw incase anyone was wondering RDM got MAB3 trait at some point
And before anyone asks yes i considered +/-enmity merits.
EDIT:
english ffxi twitterWhat's the effect “Enhances Addendum:White/Black” on SCH’s Empyrean body? W/o going into too much detail, it’s related to your enmity. #FFXI