Just remove healers.

[Martynek]

So what? The people I play with tried ninja and didn't like it; I personally haven't particularly enjoyed any of the melee DPS classes I've played. But you don't see me advocating removing melee DPS.
Other people like things you don't. Get over it.

You are not being forced to include Ninjas in your groups to be able to play the game. You are, however, forced to bring a healer. What if I want to play the game with my friends, but none of us want to play a healer? Should we just have to give in and knowingly subject one another to mental torture?
Other people do not like the things you do. Get over it.
This is a problem here because the healing role is so absurdly homogenised to the point that there might as well be only a single job within it - To further elaborate on that:

I want to put together a group for a raid.

I do not want to play a job that has frantic, high APM weaving windows every minute. I do not have to bring a Gunbreaker.
I do not want to play a job that has a rotation that is almost entirely expressed through powerful GCDs, with very infrequent usage of oGCD attacks. I do not have to bring a Warrior.
I do not want to play a job that fights exclusively in melee, with no way of keeping active at a distance. I do not have to bring a Monk.
I do not want to play a job that has a large amount of reliance on RNG to determine the flow of its rotation. I do not have to bring a Dancer.
I do not want to play a job with long cast times and little freeform mobility. I do not have to bring a Black Mage.
I do not want to play a job that spends 90% of its time pressing a single button, and another 9% of the time keeping up a single DoT. Well too bad, you WILL bring two healers. This is not optional.

So. Remove the healing role and improve the defensive toolkits of the remaining jobs to allow them to do without. It wouldn't even take a drastic redesign of the game systems or content.