I figure someone else must have noticed this, but applying several overlapping debuffs breaks, quite often.
Apply a prone debuff to an enemy. Before that debuff expires, apply a petrify debuff to the same enemy.
Result: After prone wears off, the enemy will stand up and start attacking you, despite showing the petrify debuff as still active.
This also happens if you apply a prone debuff twice. Instead of the newer prone overriding the duration of the older prone, the enemy will simply stand up and start attacking again (despite being under the effect of the second prone).