We cannot keep adding more healing abilities until we have enough outgoing damage for the heals we already have, because right now we have way too many for what the game asks of us. Not to mention the burden of knowledge is already too high for the average player to even keep track of all the different heals available to them.
We cannot keep increasing the damage of each healer's spammable attack spell, as that continues to pressure healers more and more to have as close to 100% DPS uptime as possible. We should actually be reducing the damage of each spammable attack spell by redirecting that potency into new attacks to relieve that pressure because it's way too high as it stands.
Healers should be rewarded for improving, but instead they're punished with miserable gameplay. No other role would tolerate playing a level 4 job at level 90. Why should healers?