I do think its similar to abyssea in that the mob choses an ability to be proc'ed with at time of pull because holding some mobs at time of pull and trying to stagger then by spamming dia for example won't work. nor will holding them spamming DNC JA.
For example i spammed all /DNC JA's I had on a mob for 10 mins today. DRk walks up, weapon bashes PROC! lol I think its more that then anything.
Unlike abyssea procs are NOT 100% and you can proc during 2hr, spell cast and WS use of enemy, so this is confirmed as a SAM used its 2hr and I staggers with Blade: ten right away.