Well, there's 3 skill levels generally.
10-8 Healers that can dps perfectly satisfactorily while keeping the group at stable, if not necessarily healthy, levels of HP.
7-4 Healers that can keep the group in perfectly good health, but aren't comfortable adding in dps for whatever reason, but are still capable of clearing content in a timely manner
3-1 Healers that struggle to balance their healing and dps appropriately, causing numerous needless wipes, deaths, and possibly even enrages because they lack the skill to even perform the absolute minimum required for their job, causing significant dps loss from the group as a whole despite trying to add in their own numbers.
I just find it funny that people are trying to argue that people failing at both primary and secondary responsibilities are somehow better than those capable of satisfying their primary requirements with flying colors.