If anyone was expecting a certain minimum otuput then you would be correct
People do expect a minimum dps output from Tanks/Healers/DDs, though. No midcore-to-hardcore static or majority mentality based group is going to not kick a Tank/Healer/DD is they aren't putting out at least a fair percentage of what the top-tier players are outputting. People use ACT/FFlogs. That's a fact.

I don't think it is a new thing to MMOs (or any game) to expect equal contribution in group activities.
I don't mean to be rude, but over the course of MMOs, resource management has been a thing, as has varying levels of throughput and amounts of HPS/DPS needed to meet certain criteria (i.e. to keep everyone alive and/or not cause a soft/hard enrage). FFXIV is very leniant by comparison. If you ever played WoW for it's duration, then you'll understand that a Healer was there to heal, a Tank to tank, etc. I'm saying that the traditional understanding of what each role does has evolved in the genre. To me, this is a situational problem and not one which should be forced or ingrained into new players' minds when they START the game, but, it's something to think about if they want to speed up a run or down a boss. There are valid arguements for both sides, but it's down to player preference and allowing people to ease into that mindset, rather than buldgoning new players or casual gamers. Intentions of groups/statics can be formed prior to engaging content. That way people can either up there game or just languish with what they prefer.