Actually, no, there was a huge difference.
I had a leveling static where I played PLD, and we had a THF and a SAM. At lvl 33, the more famous skillchain was Tachi: Enpi - Viper Bite, used with Sneak Attack and Trick Attack.
The thing is, SA+TA-VB was so powerful that keeping aggro on that was very difficult. So, frequently, the SAM provoked the mob away from the tank, so that the THF could align behind the tank and behind the mob.
But, if you knew how to hold aggro really well, you could keep the mob on you, while the THF stayed behind the mob and the SAM, and the mob wouldn't turn around.
In FFXI, DPS were much more powerful but were limited by how many enmity the tank could generate. When you ended with a good tank as a DPS, you really felt like you didn't have to hold back and it was a great feeling, for the tank and for the DPS.
Of course, it does, since everything people complain about is the lack of DPS. PLD's only adjustement during 3.x was to improve its DPS despite still supposed to be "the tank that mitigates". It's not that complicated to design them with another goal and still achieve similar results.
That's exactly how tanks are now. You always rely on the healer to keep you alive. As a PLD, let me be a turtle, let me rely less on the healer to survive, since surviving is supposed to be my thing. And you can keep your WAR as the sturdier DPS.
No, it's mostly because the fight design makes it too easy to heal them inbetween tank busters, even if they stay out of tank stance.
Yes, it is required. But having high personal DPS is not the only way for tanks to contribute in increasing the raid DPS. If DRK could provide TP and MP refresh with some of its skills, then MCH and BRD wouldn't have to sacrifice their DPS. If PLD mitigates enough (for him or by helping the MT) so that one healer can go 100% Cleric Stance (unless shitty situations) or even replace it with a fifth DPS, PLD's mitigation would improve raid DPS.
Just don't narrow the party's dynamic to one way when we have so much jobs...