Not necessarily true. Tp is only important if you play a class which actually requires it. The frequency it's used should be no where near ballad's unless you have mostly all melee. As oppose to healing which takes mp no matter what type of healer you have. And I don't see how the way you play t8 is moot when it actually defines what skills you actually need.
We play more paeon than ballad. Why? Because if you healers know how to heal efficient they will only need ballad in t9 (golem phase you can ballad while no golems are up so you don't even lose dmg that way). This changes ofc if people start making mistakes and die. But as long as everyone stays alive there should be no need for ballad in 6-8 even with a ilvl 90 healer.