Actually, this is not technically true.
In terms of combos, WAR's Enmity combo is actually higher potency than its "DPS" combo.
Heavy Swing > Skull Sunder > Butcher's Block is 160 > 210 > 300 potency.
Heavy Swing > Maim > Storm's Path/Storm's Eye is 160 > 200 > 280 potency.
Just, Storm's Path randomly gives 20 Beast Gauge instead of Storm's Eye and Butcher's Block's 10. So more Gauge means more 520 potency Fell Cleaves (Which means more Infuriate which in turn means more Fell Cleave...)
DRK and PLD have DPS combos that deal more damage than their Enmity combos thanks to Royal Authority and Syphon Strike (Rage of Halone combo out damages the direct damage of Goring Blade and Power Slash is equal in damage to Souleater, Syphon is just the major culprit with not only dealing more damage than Spinning Slash, restoring MP for more Dark Arts and thus more damage but it benefits from DA itself to boost its damage)
That's why change is suggested.
Comparing healers output to our DPS output is meaningless. You have to compare healers output to NPC output. As, in PvE you're not taking the damage the BLM is dishing out, you're taking the damage the BOSS is dishing out.
In any case, it's a mixture of both the output of healers and the passive mitigation from tanks.
Tanks take so much less damage passively compared to other games. In addition, healers have such massive outputs that they can easily heal large chunks of a Tanks health with 1-2 heals.
Also, if we're comparing CD's, let's not pick the classes that notoriously have few CD's:
DK:
Anti-Magic Shell: 1 minute CD (Can be talented to 45s CD) absorbs 30% of your max health worth of magical damage.
Vampiric Blood: 1.5 minute CD increases max health by 30% and healing/shielding received by 30% for 10 seconds.
Dancing Rune Weapon: 2 minute CD 40% increased parry rate (Parry in this game is also 100% damage mitigation, not just 20%)
Icebound Fortitude: 3 minute CD 30% less damage taken for 8 seconds.
Purgatory: 4 minute CD upon death instead gain healing absorb shield equal to the amount of overkill damage for 3 seconds. If this isn't healed off then you die.
Vs FFXIV:
Rampart: 1.5 minute CD 20% less damage taken (For 20s)
Anticipation: 1 minute CD 30% more parry chance for 20s (Parry only being 20% damage reduction not 100% damage reduction)
Sentinel/Vengeance/Shadow Wall: 2 minute (3m for Sentinel) CD for 30% damage reduction (40% for Sentinel)
With then Equilibrium/Shake it Off/Raw Intuition/Bulwark on top.
Really, the only really notable thing with CD's is Holmgang being a complete tankbuster ignore with only a 3 minute CD (Hallowed Ground is less obscene given it has a 7 minute CD)
But even then, they're matched by WoW Paladin with Ardent Defender's 2 minute CD 20% less damage taken, if you are killed while active you're instead healed to 20% max life, Divine Shield 5 minute CD immunity for 8 seconds and taunt all nearby enemies to attack you for 8 seconds and Lay on Hands 10 minute CD 100% max health heal.
The major difference between FFXIV and WoW tanks is that WoW tanks need to be constantly using active mitigation with often a dedicated "Tank Healer" providing them with continuous healing in order to survive to the tankbusters which require them to have a big CD available for (Or a healer has to have a big CD available to mitigate damage for them)
As opposed to FFXIV where damage is basically non-existent except for these tank busters where you're practically free to use any CD's you want because you didn't need them for any damage between the last tankbuster and the current one even while you were sat in DPS stance and mashing DPS combos.
Due to high passive mitigation and massive throughput from Regen/Shields that allow healers to focus mostly on dealing damage.
But at the same time, designing the new tank to feed into this "Damage is irrelevant outside of Tankbusters" and "Just play as a Beefy DPS because your passive mitigation is nuts" offers little itself and in fact just causes more work to need to be done if an overhaul to the game balance is done in the future.
It's also worth noting that this issue stems entirely through scaling too. Given that when you're leveling up and so don't outgear content, then balance is fine. Tanks take plenty of damage and often need to be in Tank stance and roll CD's to keep incoming damage down, while Healers will often be focusing too much on spamming out GCD's on heals and managing their mana to push out much DPS.
Only when you start to get into the wonky end-game scaling does it transition into this "Tanks are Beefy DPS" and "Healers just use oGCD's for healing" scenario.