Dispel and Spell Purge say they can dispel barrier and other beneficial effects on the affected enemies. Moreover, Spell Purge can deal a huge chunk of damage to them when dispelling with a upgrade.
However, I don't remember that I have seen any buffs on the enemies. Is there enemy buffs in this game, or it is just another fluff text? If the buffs exist, what are they?
Red Templar Horrors "charge" each other up with that red sparky "juice" stuff. I think Dispel/Spell Purge knocks that down, but I'm not 100% sure.
It's not much of a stretch to include Venatori flaming array mines as a beneficial effect, and Dispel/Spell Purge zaps those for sure.
A well-timed and perfectly targeted Dispel will cancel certain breath attacks by dragons. Like Kaltenzahn's freeze breath.
Of course, Dispel and Spell Purge can zap rift demons before they spawn in the second wave of a rift attack.
All the ranks of Terror do a weakness AoE -- not an actual buff but an effective buff, which Dispel/Spell Purge works on.
Finally, Dispel/Spell Purge clears any debuffs on your own peeps, so that's something.
I'm sure there is more. Some unique bosses have "beneficial effects" that might be susceptible, but I don't have time to research in Wiki.