I'm bundling some quotes here since they are both relevant to the reply below.
That's one of my main arguments as to why I believe changes are better directed at the AST.As far as the speculation in your latter part of the post goes - that is some really heavy speculation, but I am not saying it is impossible. [...] with the issue with AST rising up again.
[...] Let's say Scholars are the ones next who will have enmity issues [...]
If a healer (actually, pick any job, it still applies) as an entity has runaway problems or scaling issues regarding enmity, mana, healing output, DPS, etc. then the solution should not be making changes to the various pieces of content it is pitted against - it is the job itself that is broken. And it means that every time something new is introduced, this internally unsound job can run into problems that requires another fix. It is better in the long run to have a well-designed job that scales well and handles new things well than making changes to wider systems in order to accommodate inconveniences such as this. The better a job is designed, the fewer changes will be needed in the future.
If Squeenix introduce new jobs with the same issue as old jobs had before they were addressed, then Squeenix need to take a hard look at their design team, 'cause someone is in that case making the same mistakes over and over again.
And to highlight a final thing: changes made to a job does not automatically equate to that job being homogenized in relation to other jobs. Two jobs can achieve similar end results with vastly different tools. If the one can only see homogenization as a solution to making all jobs viable, it's time to take a step back and look outside of the box.
Foregoing the displacement enmity change does also not exclude playing your job and pushing for extra DPS both among tanks and healers just as before and provoking back the boss when it returns. I don't understand the notion of healers becoming the main target for a moment without dying being the worst thing in the world (doubly so if it is consistent and you can plan for/around it). We die on purpose to circumvent mechanics, we run into danger to build LB or improve DPS uptime, all these peculiar sacrifices and inconveniences - but this one is for some reason unbearable.