Well then you'd more accurately have for tanks:
dps/buff/cure/dots/mitigation/hot/etc.
But if we laboured on that then we'd miss the point.
The attitude seems to be:
Healers should heal not do anything else. The devs have made comments multiple times to reflect they'd rather healers to have more healing focus and have stripped our non-healing capabilities and added to our healing capabilities. And there is some level of community attitude that healers shouldn't DPS they should only heal, that's their job.
But the reality is, it's a team effort and jobs can contribute in different ways. As a Paladin, when a healer has struggled, I've helped with Clemency. In one particular case where the healer had connection issues, he offered to drop, I told him to carry on because I could help with the healing.
As an off-tank, if my main tank is struggling I can help mitigate damage.
As a tank if a DPS is taking incoming damage I can help mitigate their damage and also heal them.
As a RDM, if people are dying, I can help out the healers with raises. If it's really bad I can help with the Cures.
As a DNC/MCH/BRD I have skills that mitigate damage, not just the tank, which applies to the whole party.
As a SMN, I can also mitigate damage with the right pet.
Heck, if you sustain aggro, in an emergency you could technically off tank on MNK, which I've seen happen.
There's lots of ways people can contribute outside of the scope of their role and it's good to have, because it's more dynamic.
With healers it seems the attitude is for them not to?
Yet, they have the tools to do so, even though those tools are gradually being stripped, despite the fact we have this big gap where we can be using them and it's really unengaging to.
Whereas technically all a tank needs to do to be a good tank is take damage and keep others from being damaged. They could do have a simple "1, 2" DPS rotation and still achieve their duties. Yet, they get a more engaging set of DPS skills to work with, not as engaged as a full DPS, but tanks have focuses normally DPS's don't and I feel this is where we should be with healers. In fact, we /used/ to be there with healers.