Here's my personal list:
Affliction rate > Atk > Def > HP > Affliction resist > Ability damage > Mode Gauge > Burst damage
For ability damage however, I guess the rare exception would be to stick it on himes with strong multi hit nukes (SSR Artemis for example). Still, not sure whether I'd go for it actively, more like if you had an accessory with 2+ ability damage, there's the option if you don't have anything better.
As for drop rate up... I abstain from ranking that. Every little buff in drop rate counts, but I'm not so sure you'll want to afford that while the powercreep updates are coming soon...