Party Frames need to be modified to be customizable. This includes not just what appears on them, but also having the ability to choose from a variety of appearances for the actual Party List. This is important for healers, as I know a few people who dislike how the party List looks, and in fact greatly prefer the ALLIANCE List for its simplicity, albeit a bit bigger would be good for the purposes of the primary party list.
The goal here is to allow options for the player, but also to provide options that give more visual clarity than currently exists. As a singular example, perhaps you set up an option where you only see CLEANSABLE debuffs appear on the party lists, so the healers can just quickly see if there are/aren't any to cleanse. It allows them more time to focus on the fight, and less time trying to make sense of the info on the Party List.