The fights are designed to be cleared without healer DPS only (1) after the party is over the item level that is available to them when the fights are added to the game and, even at that point, (2) when all DDs and tanks are doing at least 85-90% of their optimal DPS (while the non-dpsing healers are pulling way less than 50% optimal performance...). So it's extremely misleading to claim the fights are very much clearable without any healer DPS. Even Yoshi directly said that healer DPS is needed when the fights are added to the game.
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.
Also, once again, it isn't relevant what is said about the game, it's relevant how the game is actually played (it doesn't matter if someone would say the fights can be cleared without healer DPS when in reality you often do need it, and even if you don't it makes absolutely no sense for the healers not to DPS).