Here:
Source: https://www.bluegartr.com/threads/12...-Event-5-19%29Yoshida: Yes. Since all DPS jobs will be increasing up through level 60, it makes sense to have the white mage's DPS extend by a proportional amount as well. For development, such as with Bahamut's Coils, the development team assumes what the item level should be for general equipment on players when they clear a raid. They sum up the basic DPS for four DPS and tanks at that assumed item level and cut that by about 10-15% for the minimum clear DPS. Healer DPS is not taken into account when this is set.
Certainly for people who are at world's first level, their goal is to clear it at as low an item level as possible, lower than the one assumed during development. So if you look at the fight and figure out that if it's not numerically possible to clear with four DPS and tanks, you'll need to make up the gap with DPS from healers.
So when you're saying "fights aren't balanced for healer DPS", remember they're not also balanced to be beaten without it at the item level available to players when they are released, and by Yoshi's own admission this gap has to be filled with healer DPS.
But this play style you're advocating means the healer is playing extremely ineffectively, not using or even throwing away all the resources they have to boost the party DPS (through not boosting their own healing with cooldowns so they can DPS more, and also not doing DPS themselves and not boosting their party members' DPS either, causing the fight to last longer). How much wasted DPS does this play style cause, and how many team members and how many times would the healer have to rescue (in a way that wouldn't be available for the healer if they hadn't been saving their resources / not DPSing) to make up for it in a situation when things would go wrong (when they often won't or at least shouldn't)?