Pretty much this. But it’s not just staying near them that causes it. For example, if you just afk near one and don’t leave it’s range, you won’t see the bug. Going in and out of the dancer’s range or taking damage/corruption while under the Entertained buff can cause it to trigger. In my screenshots showing 70+ healing per second, I was in a corruption area for a while. The healing was stacking really fast.
If I play normally outside of a corrupted area, it still bugs but doesn’t stack as quickly.