Not sure if this is tracked, but the top MC healing parse and probably a few others are using the spiritual healing - respec bug.
You can see the renew ticks for ~460 but this is only possible with deep holy and 1300 healing power (not attainable currently)
https://classic.warcraftlogs.com/reports/T9crHGm84vJ6kadz#fight=52&type=healing&source=4
Currently still a bug in game but hopefully we get a fix soon