http://www.pcgamer.com/after-further-review-divinity-original-sin-2s-infinite-damage-loop-is-being-removed/

I was surprised yesterday when Divinity: Original Sin 2 producer David Walgrave told me that the damage loop seen in the video above would not be removed. "It appears that it is not a never-ending loop and you're not doing anything else while you're doing it," he wrote. 

As you can see in the video, however, the trick cycles through a feedback loop that drains a troll's entire health bar. (Head to yesterday's story for an explanation of how it works.) So even if it is within the confines of Original Sin 2's spell logic, it's just a tad OP.