The broken FFXIV Holy trinity

[Zfz]

then why do we have cleric stance.

So people who start their character as healers aren't getting the short end of the stick.

Yoshi-P publicly said that encounters are balanced without consideration to healer dps at all. They are just leaving that option open for people. Healers can DPS. But the design intent was not that healers are supposed to DPS.