Reasoning for removal of TP, but not MP?

[Seraphor]

We were talking about AoE spells which require a resource to prevent AoE-spamming, correct?
Holy is no healing spell, it does damage, and unlike TP classes hasn't got his cost removed.

Why not?

Because it's not the same.
It's a healer using DPS spells. That's their whole MP management shtick.

Healers: Manages MP by balancing DPS vs healing, their role vs bonus damage.
RDM and SMN: No MP issues unless they raise, stepping outside of their role.
DRK and BLM: MP management integral to job mechanics.

Physical DPS are the only ones who were arbitrarily gimped for doing their core job role too much.