Not actually an ability pack, but whatever.
Damage Tracker
If you've playtested Boss Battles 1.2, you might know what this is. It works well there, why not here?
Players can type in /ff2dmg on to enable it, gluing the top three damagers to the top left of their screens. /ff2dmg off to disable, /ff2dmg # to change the number of shown slots. Maximum is 8.
Be sure to tell clients how to use it (ex. if you have Advertisements, add a line for /ff2dmg) or it'll just sit on your server like a slug.
Threaded Mode