Regardless of role abuse is unacceptable. 2 things which would instantly remove much of the abuse towards players

1. Provide healers with ability to flag an abusive player in the raid/party frames (tick box) If the flag exists then a status change to be placed on that character so that they cannot receive heals from the player that has flagged them, also possibly adding a graphic for all to see flag placed .. name and shame! is perhaps another option.
2. Add a right click report facility for all players which would not only report the abuser but also send the last five minutes of the chat log so that they can instantly see on receipt details. It can be difficult to continue playing, taking screen shots and filing reports in instance while the abuse is rolling - this would resolve that.