After the 15.06.2018 patch the health regen buff is still glitchy.
patch notes: “Fixed a health regen issue which could max your health after taking damage under certain conditions” PC Patch Notes (15.06.2018) Build 100728/18311
The health regen buff no longer stacks up to arbitrary high amount and is no longer semi-permanent, but although health does regenerate while in range of a dancer, the buff icon can still disappear and reappear while in range, it does not show up in the character stats window and “effects” (which can show up in duplicate) indicates “entertained: health regeneration 0%”.
It looks like the underlying cause of the OP regen bug was not (completely) fixed, instead a band-aid was put on it.