Some debuffs will just plain not show in 24 man content.

For example, I have only my debuffs set to show on the target. Despite that, in any world of darkness run it's not uncommon that even when my touch of death, dragon kick, or demolish connect, sometimes the debuff will not show up at all even if the damage is still ticking.

It's even more crippling if you play a summoner because you need to keep track of your dots and it's kinda aggravating not being able to and you need to fester and it's a guessing game whether the dot is still up because even reapplying the DoT may not make it visible.