It makes sense thematically. Tanks and DPS are fine in solo content because of their sustain and damage respectively, while healers are worse in both categories. It's also a step in the right direction for what healers want.
You could leave tank damage where it is so they're not shafted and put healers around 30% above them toward DPS levels, but asking them to rebalance the entire game around that is futile when they won't even rebalance old duties to match the current meta.
"Why not both?"