It's not a black and white issue, but you're more wrong than you are right.
Fights are not just about raw HPS. A person who has no idea what they are doing can top the HPS meters spamming their largest heal on the tank who is taking the most damage. That doesn't make them a better healer than the person who knows how to conserve mana, makes the most efficient choices about which heal to use when, and who to heal first.
The rankings can be a useful tool for determining who is doing well and who is underperforming... if they are used correctly and interpreted within the context of the fight and the assignments given. This is not a matter of "person on top is good, person on bottom sucks."