Yet it has gone overboard to the point that tanks no longer need healers at all, and they don't need damage dealers unless there is a DPS check to beat that tank DPS can't handle.
If a tank dies, the healer has the ability to resurrect the tank quickly (if they haven't just used their Swiftcast), tank can provoke as soon as they're up and wipe is averted.
If a damage dealer dies, the healer has the ability to resurrect them quickly to contribute to any DPS check the party needs to pass to avoid a wipe.
If a healer dies, who is there to resurrect the healer? Either the party has RDM or SMN, or the healer remains dead.
The answer isn't to give other roles multiple tools to handle healing and mitigation. The answer is to give the other roles a tool to resurrect the healer so they can perform their role just as the healer is able to resurrect the other roles so they can do theirs.
That's not to say that the other roles should have no tools for healing and mitigation. But those tools should be rare with moderate length recast time (90-120 seconds) and should apply to self only (outside of tanks getting a party wide mitigation tool to use, which would be appropriate for their role).
The utility that damage dealers get should be related to dealing damage. Increase the damage done by self and party members. Debuff the boss to reduce their damage dealt and/or increase damage taken. I'm old school enough I would love to see crowd control make a comeback for some boss fights and having damage dealers responsible for that.
The job design team needs to step back and remember the point of each role in the trinity. Tanks generate enmity so the majority of incoming damage is directed at them, then mitigate the damage received so they can survive long enough to get needed healing from healers. Damage dealers deal damage to all enemies while doing their best to avoid avoidable damage. They likewise should be relying on healers to handle unavoidable damage plus any additional damage taken due to errors.
If they're going to keep giving a single role more and more tools then design encounters so the other roles are only relevant to speed of kill and not to success, then they need to get rid of the trinity entirely and give all jobs the same general tools with the same overall potency/power as those that tanks are being given.