This log contains exploits, the three warlocks cast only lifetap during Magmadar to allow Dissa to be able to spam prayer of healing to obtain extremely high hps.
https://classic.warcraftlogs.com/reports/AH4g7GNzWKtC3n1M#fight=2&type=healing
https://classic.warcraftlogs.com/reports/AH4g7GNzWKtC3n1M#fight=2&type=casts&ability=11689